Part II - Methods of CIL Interpretation in International Courts

5 The Application of Logic and Reason in CIL Identification and Interpretation

William Thomas Worster

1 Introduction

The process of identifying and interpreting norms of customary international law, while appearing to be primarily based on an inductive analysis of state practice and opinio juris, is sometimes a deductive exercise based on logic and reason. Logic permeates every decision in international law. Illogic might also be present as well, of course, but in terms of identifying, interpreting, and applying law, we tend to claim that we do it logically and, perhaps, even scientifically. Logic manifests itself inherently throughout the process and can be identified in all steps of reasoning in identifying, interpreting, and applying customary international law. Logic, however, can constitute the application of either an inductive or deductive inference. This chapter will focus on situations in which the International Court of Justice (ICJ) and Permanent Court of International Justice (PCIJ) applied a deductive approach, identifying or interpreting norms of customary international law without seeming to consult state practice and opinio juris. Specifically, it will consider whether norms that can be reasonably inferred or deduced from existing rules, or that are simply logical for the operation of the international legal system, can be identified as norms of customary international law under a complementary, supplementary, or distinctive interpretive approach.

One initial observation is necessary at the outset regarding proving customary international law. In customary international law, the process of constituting or prescribing a norm, while analytically distinct from proving the existence of the norm with evidence, is often blurred with it. That is to say, we usually claim that a norm of customary international law has been created when we can prove the existence of sufficient state practice and opinio juris. We might concede that the norm could have existed prior to our discovery of it, but we would likely still insist that the norm came into being when a critical mass of state practice and opinio juris, the evidence of the norm, coalesced. In addition, we do not usually distinguish between the ascertainment of the existence of a rule of customary international law and the interpretation of the rule’s content. Generally, those operations are combined into one act of ascertaining the content of the rule through evidence at the level of its identification. In the International Law Commission (ILC) study on customary international law, the special rapporteur was careful to observe that the study was undertaken to state the rules on the identification of customary international law.¹ As will be discussed further, the ICJ as well, implicitly, distinguishes between these operations.² Thus, the proof of the norm and its creation, constitution, or prescription, as well as the development and identification of content, while they are casually unified into one act of discovery and confirmation through evidence, can be distinguished.

Part of the reason for mixing these questions into a casual unified approach is that we do not clearly state whether the state practice–opinio juris analytical framework is a question of law or a question of fact. Surely, it cannot be a question of fact, because we are not trying to establish acts that trigger the application of the law, but then why do we collect a sampling of evidence and consider its reliability and sufficiency, as if we were proving a fact? Surely, it is a question of law, but then why do we not simply allow the court to inform itself as it sees fit, jura novit curia? The difficulty is that it is law, but the content and existence of the law is established by facts. The ILC special rapporteur was well aware of this difficulty and was careful to note that he did not use the expression ‘evidence’ in the sense of establishing a fact.³ But this conclusion also means that the court is perhaps freer to use various forms – perhaps conflicting forms – of logical inferences throughout the process of identifying customary international law than it might if it was establishing facts.

2 Forms of Logic and Reasoning

What does it mean to use ‘logic’ or ‘reason’ to identify customary international law? A fully detailed explanation of logic is outside the scope of this chapter,⁴ but essentially it involves the process of drawing inferences, either through induction or deduction.⁵

Induction is usually described as drawing inferences from examples of empirical phenomena to create a general theory explaining those phenomena. The assumption is that a sample of instances will produce observable phenomena that will always be the case,⁶ based on a statistical syllogism that the overall population of cases resembles the sample pool.⁷ This inference to a theory will be more or less accurate depending on the quantity and quality of the evidence.⁸ In terms of collecting evidence, the approach uses a sampling pool of data and generalization to an explanation.⁹ However, the process of sampling and generalization is usually predicated on the sample pool being random.¹⁰ Of course, random sampling could include sampling with an equal probability of selecting a sample, sampling a number of cases from the same pool rather than a single instance (cluster sampling), or deliberately placing samples into certain subpools and randomly drawing from them (stratified sampling).¹¹

Deduction, on the other hand, begins with premises, which are either established (themselves through induction or deduction) or presumed to be true, and then proceeds to infer a conclusion that must follow.¹² Its strength is that, again, if the premises are true, the conclusion is not subject to falsification.¹³ It is not based on sampling instances or developing theories to explain those cases. There are many forms of deductive reasoning that could be characterized as logical, but several are relevant for this chapter. Talmon, for example, identified normative, functional, and analogical deductions in the case law of the ICJ.¹⁴ These logical inferences are based on, respectively, deducing the content of rules from other rules or principles, the functions of an organization or actor, or by drawing an analogy from existing rules to a situation not initially covered by the rule.¹⁵

Having surveyed the basic forms and approaches of logic, this chapter will now turn to their application in identifying rules of customary international law.

3 The Use of Logic and Reasoning in the Analysis of Customary International Law

Traditionally, we say that the identification of customary international law is a process of inductive reasoning from manifestations of state practice and expressions of opinio juris,¹⁶ but the various steps in customary international law analysis are also infused with a considerable degree of deductive logic – including both the processes to discover secondary rules and those used to discover primary rules.¹⁷ The chamber of the ICJ in the Gulf of Maine case stated that customary international law ‘can be tested by induction based on the analysis of a sufficiently extensive and convincing practice, and not by deduction from preconceived ideas’.¹⁸

But the ICJ does not necessarily follow a truly inductive process. We do not randomly identify states to examine. Instead, we select which states to sample based on a specially interested states analysis and/or a (geographic, historical, etc.) diversity of states. In either case, the states chosen are not selected by random draw, but are chosen for their ‘representativity’. In addition, induction usually establishes a prior standard for determining when the sampled cases would be sufficient,¹⁹ and sets the standard of proof accordingly,²⁰ yet the ICJ has not articulated a clear standard of proof for customary international law. More importantly, a truly inductive logical approach must find the rule negated by even one instance of contrary practice,²¹ and yet, in the Nicaragua case, the ICJ was explicit that perfect conformity was not required.²² And in the Gulf of Maine case cited above, the ICJ chamber added that, while induction is one approach to identifying customary international law, there was also ‘a limited set of norms for ensuring the coexistence and vital cooperation of the members of the international community’.²³ For these reasons, and others, many scholars have argued that a ‘modern’ approach (or ‘human rights approach’) to customary international law in fact applies deductive logic.²⁴

That being said, the actual logical reasoning applied by courts is often opaque. Sometimes it can appear that a court has deduced the existence of a rule when it may have applied an inductive approach. For example, in Maclaine Watson, the House of Lords (as per Lord Templeman) concluded that imposing liability on the states that constituted the International Tin Council when that organization dissolved would not be logical: ‘An international law or a domestic law which imposed and enforced joint and several liability on 23 sovereign States without imposing and enforcing contribution between those States would be devoid of logic and justice.’²⁵ This sentence suggests a deductive approach. However, Templeman continued to explain that: ‘No plausible evidence was produced of the existence of such a rule of international law before or at the time of the Sixth Agreement in 1982 or thereafter.’²⁶ Therefore, although it might at first appear that he was asserting a rule, he was in fact concluding that such a rule was not logical or just because it had not been proven to exist. Of course, it might be that rules of customary international law are logical, as deduced from certain values rather than induction from practice, but that the same rule would result from either deduction or induction, and deduction only buttresses the conclusion from induction.²⁷

3.1 The Foundations of Customary International Law as a Source of International Law

The very existence of customary international law as a source of international law is largely a result of a logical deduction. In the early jurisprudence of the PCIJ and other bodies, no effort was made to establish consistent state practice and opinio juris for the existence of custom as a source of law,²⁸ and instead the PCIJ and other authorities deduced the existence of custom.²⁹ Similarly, when the International Law Association sought to complete its study on customary international law, it acknowledged that it would draw on the practice of states to identify the rules of customary international law, though that was not simply an exercise in using custom to support the existence and rules of custom itself.³⁰ In the ILC study on customary international law, the special rapporteur relied almost exclusively on the case law of the ICJ, among other courts and tribunals, and cited to little state practice or opinio juris as expressed by states on point.³¹ Of course, those cases that were cited might or might not have cited to state practice or opinio juris in turn. These approaches do not make the conclusions wrong; after all, reliance on prior judicial decisions is a valid subsidiary source for the content of any of the formal sources.³² But such reliance on prior cases demonstrates that the identification of customary international law as a source of international law is not entirely established by state practice and opinio juris alone and is likely a logical deduction from the behaviour of states.

In turn, the very constitution of customary international law by state practice and opinio juris alone is also not clearly based on a logical inductive examination of state practice and opinio juris.³³ Instead, the requirement of state practice and opinio juris is primarily derived from the PCIJ and ICJ Statutes, upheld by legal tradition and reaffirmed by, inter alia, the ICJ.³⁴ From the language of the Statutes, it is not completely clear that customary international law is formed by state practice and opinio juris as elements.³⁵ There is certainly space to argue that these aspects are factors or perhaps even evidentiary measures for custom.³⁶ In fact, the process of identifying rules of customary international law often treats state practice and opinio juris more like factors or evidence than truly as elements.³⁷ Nonetheless, they are commonly understood to be elements.³⁸

3.2 The Deduction of Customary International Law without Resort to the Elements

Both the ICJ and PCIJ have suggested that some rules of customary international law might not be established by the elements of state practice and opinio juris.³⁹ As noted above, the ICJ chamber in the Gulf of Maine case took note of some norms in international law that were not proved through induction but by their role in ‘ensuring … coexistence and vital cooperation’.⁴⁰ The ICJ seems to be saying that there are some rules that are established through an inductive inference from state practice and opinio juris, but that there are other rules that are not.⁴¹ This approach is not isolated. In the Corfu Channel case, the ICJ relied on ‘elementary considerations of humanity’ to identify rules of customary international law.⁴² We could interpret this passage in an alternate way: that some rules of customary international law, while constituted by state practice and opinio juris, can be proved to exist by simply being logical for coexistence, vital cooperation or principles of humanity. And yet, the ICJ has also held quite clearly that customary international law norms cannot simply be deduced from ‘humanitarian considerations’ or ‘moral principles’.⁴³

The ICJ takes several approaches to deducing the existence of customary international law. The first approach – what Talmon terms ‘normative deduction’ – is to infer the existence of a rule from other rules. For example, the ICJ has relied on the contents of treaties to prove the existence of customary international law.⁴⁴ While it identified the right of self-determination in the Namibia advisory opinion, it used the UN Charter to interpret the rule as applying for all peoples.⁴⁵ In a similar fashion, it has looked to UNGA resolutions to prove customary international rules.⁴⁶ However, in both instances one could argue that the ICJ was not identifying a new rule of customary international law, but was instead using the UN Charter and UNGA resolutions to clarify the content of a rule through systemic interpretation. In the Territorial and Maritime Dispute, Nicaragua and Colombia agreed that customary international law would apply to the case because Colombia was not a party to the UN Convention on the Law of the Sea (UNCLOS), and agreed that the provisions in UNCLOS regarding the baselines and entitlement to maritime zones, exclusive economic zone (EEZ), and continental shelf reflected customary international law,⁴⁷ though they disagreed over the content of the rules concerning the continental shelf beyond 200 nautical miles.⁴⁸ It is possible to argue that the ICJ was merely affirming that Nicaragua had an obligation toward the other states parties to UNCLOS to comply with Article 76 when it referred to the ‘interrelated’ nature of ocean space.⁴⁹ However, it did explicitly cite to obligations inter partes between states not parties to the dispute. In fact, it argued that UNCLOS created a new ‘legal order’, so Nicaragua was under this obligation in a dispute with a state not a party to UNCLOS.⁵⁰ Thus, the failure of Nicaragua to comply with the procedural requirements of UNCLOS meant it had not established its continental margin vis-à-vis Colombia, a state not a party to UNCLOS.⁵¹ Judge Robinson criticized this conclusion, arguing that the procedural condition was not part of customary international law and could not be applied.⁵² What is not entirely clear in these cases is whether the ICJ was using the existence and content of treaties to prove the existence of a custom or clarifying the content of the rule.⁵³

The ICJ also deduces rules of customary international law from other customary international rules. In the Burkina Faso/Mali Frontier Dispute, it held that uti possidetis was customary international law because ‘it is logically connected with the phenomenon of the obtaining of independence’.⁵⁴ While this phrase might even suggest deduction of the rule from facts, actually the ICJ was deducing the customary rule of uti possidetis from the other customary rules governing independence. In the Qatar and Bahrain Maritime Delimitation, the ICJ set aside evidence of practice as inconclusive and instead deduced that ‘low-tide elevations cannot be equated with islands … or other land territory’ as they are understood under prevailing rules on territorial sovereignty.⁵⁵ Thus, in these cases another norm of customary international law formed the framework for assessing the norm at issue. And while it is debatable whether the ICJ was identifying a new rule or clarifying an existing one, it appears to apply a teleological interpretation of other rules of customary international law. This approach should not be too shocking, because domestic courts sometimes take the same approach. In the case of A v. Attorney-General, the Swiss Federal Criminal Court held that the accused was covered by the same immunity enjoyed by a head of state because, as minister of defence, he was a member of the unusual collegiate body – the HCE, or Haut Comité d’État (High State Council) – that discharged presidential authority. The Federal Criminal Court did not examine state practice and opinio juris to determine whether a collegiate presidential council would enjoy the same immunities, but reasoned that logically it would, based on the purposes of head-of-state immunity.⁵⁶

However, the ICJ has also deduced the existence of customary rules from other customary rules, not by logically deriving the rules from other rules but by analogy. In this approach, the ICJ is more clearly focused on applying customary international law rules that apply in other situations to a case where they clearly do not, and thus is more likely identifying a new rule rather than clarifying an existing one. For example, in the Libya and Malta Continental Shelf case, the ICJ identified a customary rule permitting 200 nautical miles of continental shelf by drawing an analogy with the exclusive economic zone.⁵⁷ However, this approach is not without criticism. In the Arrest Warrant case, the ICJ deduced the existence of immunities from arrest for a foreign minster by considering the functions of the office.⁵⁸ Unlike the situation of a head of state mentioned above, which clearly benefitted from a rule of immunity and needed clarification, this case asked whether the official had any immunities at all. Judge Van den Wyngaert critiqued the approach of identifying the new rule by deduction, calling it ‘a mere analogy with immunities for diplomatic agents and Heads of State’ without proper reliance on evidence of state practice and opinio juris.⁵⁹

The ICJ also deduces customary international law from legal principles. There are at least two versions of this approach. One possibility, a more conservative one, is to deduce the existence of certain principles from treaties or other customary law and then take one more step and deduce the existence of rules from those principles. This is the approach that Talmon terms ‘triangular reasoning’.⁶⁰ For example, in the Corfu Channel case, the ICJ identified the principle underlying the Hague Convention VIII of 1907 (i.e. the obligation to notify ships of minefields).⁶¹ The treaty did not specifically apply to the situation of peacetime, and yet the Court stated that such a duty also applied in peacetime.⁶² Similar to the practice of deduction by analogy, this practice appears to be focused on identifying new rules of customary international law.

One method for reasoning the existence of customary international law from abstracted principles, themselves potentially drawn from other treaties and customary law, is the necessity of the rule. As the ICJ said in the Gulf of Maine case, some rules are ‘vital’ or ‘ensur[e]’ international cooperation and coexistence, and in the Gabčikovo-Nagymaros Project case the ICJ stated that the rule was ‘require[d]’.⁶³ The ICJ has stated that the reason for this view is that it should be reluctant to find customary international law restraining state action ‘[w]hen the stakes are not as high’,⁶⁴ – that is to say, when the rules would be less necessary. That being said, the ICJ has been willing to deduce rules that are not absolutely necessary. Some rules are merely ‘important’⁶⁵ and perhaps even ‘logically connected’ to other principles.⁶⁶ In fact, some rules are simply reasonable expectations from other principles, such as the ‘elementary considerations of humanity’ cited in both the Nicaragua case⁶⁷ and the Corfu Channel case.⁶⁸

The ICJ also occasionally applies an even more liberal approach, not necessarily identifying a treaty or customary law from which to draw legal principles before deducing the existence of customary international law. This is the case in Jurisdictional Immunities, where the ICJ noted the important principle of sovereignty and its derivatives sovereign equality and territorial sovereignty,⁶⁹ and in Certain Documents, when the ICJ took note of the principles protecting the integrity of legal proceedings.⁷⁰ Such practice can even be identified in the Lotus case, where the ICJ stated that ‘[a] corollary of the principle of the freedom of the seas is that a ship on the high seas is assimilated to the territory of the State the flag of which it flies, for, just as in its own territory, that State exercises its authority, upon it, and no other State may do so’,⁷¹ and in the Pulp Mills case the ICJ observed that ‘a precautionary approach may be relevant in the interpretation and application of the’ treaty and then stated that the treaty ‘has to be interpreted in accordance with [what] … may now be considered a requirement under general international law to undertake an environmental impact assessment’.⁷² Perhaps the ICJ could have identified treaties and other custom that evidenced such principles as applicable, but that step was omitted.

In other cases, the ICJ does not deduce the existence and content of a customary rule from a treaty or other source of law, nor deduce principles from those sources, but instead deduces customary rules from the logic and reasoning, the underlying purpose, of the rule itself. As such, the particulars of the rule applicable in a given case might be merely characterized as explaining the content of the rule in more detail, rather than identifying an entirely new rule. In the Western Sahara and Wall advisory opinions, the ICJ deduced from the existence of the rule of self-determination under customary international law that its full scope of application was erga omnes,⁷³ again with little regard to state practice and opinio juris.

One the one hand, the ICJ appears to use deduction of rules quite often, yet, on the other hand, insists that it does not simply deduce rules.⁷⁴ A possible explanation is twofold. First, in many of these cases the ICJ is not necessarily deducing the existence of new rules but rather interpreting the content, scope, and application of existing rules. For example, in the Arrest Warrant case, one could characterize the rule as being immunity for certain high state officials, with head of state being a clearly established example and foreign minister a less clear example. The ICJ did not discover a new rule of immunity of foreign ministers, but instead clarified that the scope of high state official immunities covered them. State practice and opinio juris was not necessary for these narrow cases, because there was already well-established state practice and opinio juris for the functional category in which foreign ministers fall. In a similar manner, the extension of customary international humanitarian law to cyber operations might not call for supplementary evidence of state practice and opinio juris, because there is already solid evidence that these rules apply to armed conflict through whatever mode it is manifested.⁷⁵ This view can be justified by recalling the distinction between the identification and the interpretation of customary international law. Where the ICJ is identifying a new and distinct rule, perhaps it must locate state practice and opinio juris, but when it is merely interpreting the content of the rule, it is freer to use other legal interpretative techniques such as analogy and the context of other legal rules. That being said, the line between identifying a new rule and clarifying the content of the rule is so fine that the distinction is admittedly difficult to draw, potentially opening the door to more flexible interpretative techniques. Given the ICJ’s affirmations of the state practice-opinio juris rule, we could conclude that when it applies deduction in this manner, it is presuming what state practice and opinio juris it would expect to find, had it looked.

Second, we can also recall the distinction between the formation of customary international law and evidence for the formation. Several authorities have argued for the use of deduction when determining whether there is sufficient evidence for customary international law. The ICJ could be deducing the probable existence of certain rules and then lowering the threshold of evidence to establish the rule (perhaps even reducing it to zero in clearly obvious cases), rather than deducing the existence of customary international without any regard to state practice and opinio juris. In essence, some norms are simply more obvious,⁷⁶ because they are logical or necessary for international cooperation. In his dissent in the North Sea Continental Shelf cases, Judge Lachs stated that deduction is an alternative to induction when the norms are difficult to prove.⁷⁷ Certainly, the ICJ appeared to take this approach in the Asylum,⁷⁸ Nicaragua,⁷⁹ and Qatar/Bahrain Maritime Delimitation cases.⁸⁰

However, the ICJ does not confirm that either of these explanations is correct. More often, it dispenses with a lengthy explanation, or perhaps any explanation at all, of the evidence on which it based its decision, leaving obscurity over whether deduction was the sole basis for the rule, a supplementary basis, or a reduction in the burden of proof through inductive means.⁸¹ For example, in the Arrest Warrant case the ICJ simply stated ‘it is firmly established that’.⁸² Use of the term ‘established’ can probably be assimilated to ‘proved’, although even if it was a synonym for ‘constituted’, the ICJ is still referencing confidence in its existence, which is an evidentiary matter. In the Gulf of Maine case, the ICJ expressly stated that there were two classes of rules of customary international law, proved by induction and by deduction.⁸³ In the Corfu Channel case, the ICJ quite clearly drew on considerations of humanity as the reason for its conclusion, not as a basis for deducing the scope of another rule of law.⁸⁴ If it truly was simply a lower evidentiary burden, one would expect the ICJ to use different phrasing to describe what it was doing. While we might attempt to overlook the Corfu Channel approach because it emerged during an era when international law might not have been well developed, the Gulf of Maine case was decided in 1984.

Most likely, the best explanation is that, in principle, state practice and opinio juris are required in all cases. However, when a norm is necessary (or at least logical or sensible) for the international legal system, or a parallel treaty is in place that governs the parties, or the question is really just a clarification of the scope of an already existing general rule of customary international law, then the ICJ can deduce that it is safe to presume state practice and opinio juris, and an inductive analysis with evidence is not necessary. The rule is simply very obvious in such cases. Other, more novel, situations demand stronger evidence of state practice and opinio juris. While the distinction between these two approaches is more likely a spectral one, reducing the need for compelling evidence in proportion to the reasonableness that the rule exists, the ICJ in Gulf of Maine identifies the two ends of the spectrum. Thus, the ICJ is not necessarily inventing customary international law from whole cloth by pure deduction, assertion, or arbitrariness, but instead identifying rules that are more likely than not to exist, and more likely than not to have certain content, when operating within an environment of other rules of international law.

3.3 Deduction of Customary International Law within the Application of the Elements

Of course, this analysis means that the ICJ still makes use of inductive reasoning. In many cases, it does apply state practice and opinio juris as elements that are used to identify legal rules. Following from Section 3.2, where logic and reason could be justifications for an abridged inductive analysis, this section discusses the assessment of evidence for customary international law in the inductive process, and again we find the use of logic throughout the process.

Initially, it could be that the states disputing a matter might simply agree on the existence of a rule of customary international law.⁸⁵ If they stipulated this rule, then it would govern the dispute and, especially if used as the basis for a decision by the ICJ, would control the outcome. This outcome would stand, even if the norm of customary international law later appeared to be unfounded in state practice or opinio juris. After all, some of the votes of the ICJ on questions of the existence of a rule of customary international law have been rather close.⁸⁶ For its part, the European Court of Justice has also taken the position that the parties must contest the existence of a customary international law rule or it can be presumed to exist.⁸⁷ Pellet and Gaja have both argued that acceptance of a rule of customary international law is not required by states, so whether states accept the existence of such a rule in a dispute between them is not a requirement.⁸⁸ The question in this chapter, however, is the reverse. While acceptance is not a prerequisite for the existence and application of the rule, in the sense that refusal could block creation and application of the norm, acceptance does appear to be constitutive of the norm, at least insofar as the norm is applied in the dispute and serves as precedent for disputes that follow. Pellet argues that acceptance is not constitutive, but instead merely eases the burden of establishing the existence of the rule in the dispute.⁸⁹ Here again, the distinction between the existence of a rule and the evidence of a rule appears.

In a similar fashion, for some states the views of their foreign ministry might preclude any ascertainment of customary international law. A state’s internal determination by its foreign ministry on the existence of the customary rule might be determinative that a rule exists under customary international law, be it in operationalizing its foreign policy or for settling a dispute of international character within its domestic legal system.⁹⁰ Again, such a determination might not be supported by adequate state practice and opinio juris. Such a decision by a domestic court might in turn be used elsewhere as evidence of the existence of the norm. The ILA concluded that the differing views of the executive or legislature on a customary international law norm would have different weight, but that neither was necessarily excluded.⁹¹ However, when the question of the norm is raised within a domestic situation, the executive’s position might be binding on a court.

When states disagree over the existence of a rule, then the ICJ may take a more scientific inductive approach, but this approach should not blind us to the use of deductive logic within the application of induction. The dispute serves to frame the question about the rule and, as such, already impacts the form of the rule, as states suggest competing hypotheses and the decision-maker needs to adopt one or the other hypothesis.⁹² Important to note, however, is that the competing hypotheses are themselves not necessarily the outcome of inductive logic but could be based on deduction from other principles or aims. Evidence of state practice and opinio juris that does not support one or the other hypothesis can be disregarded.⁹³ In this regard, Judge Van den Wyngaert’s dissent in the Arrest Warrant case is important, for there she challenged the framing of the hypothesis by the ICJ:

In technical terms, the dispute was about an arrest warrant against an incumbent Foreign Minister … In a more principled way … [i]t was about the question what international law requires or allows States to do as ‘agents’ of the international community …

The Court has not addressed the dispute from this perspective and has instead focused on the very narrow question of immunities …⁹⁴

Whether there is any presumption in favour of or against the formation of a rule of customary international law is also deduced logically. In principle, we might apply the Lotus presumption against states binding themselves, but the ICJ has suggested that UNGA resolutions on point can create a presumption in favour of customary international law.⁹⁵ Instead of a presumption, it might simply be that UNGA resolutions are weighty evidence.⁹⁶ Also consider in the Navigational and Related Rights case, where the ICJ found the existence of particular customary international law because Nicaragua failed to object to a long-undisturbed practice.⁹⁷ It is difficult to understand how the ICJ believed a Lotus presumption against custom had been overcome in Navigational and Related Rights with such weak opinio juris and – as it admits – not well-substantiated practice. In essence, the ICJ used logic to interpret the meaning of silence.

Logical deduction is also largely the basis for determining the types and forms of evidence that the ICJ and other authorities accept for the purpose of identifying customary international law. As a preliminary matter, the limitation of practice to acts of states, rather than international organizations or other actors, is largely traditional. The ILC special rapporteur cited little actual practice of states to support his conclusion that international organizations contribute to customary international law ‘[i]n certain cases’ and that we should approach the question with ‘caution’.⁹⁸ In addition, whether actors within a state engage the state’s role in constituting customary international law is often assessed by analogy to either the Draft Articles on State Responsibility rules on attribution⁹⁹ or the Vienna Convention on the Law of Treaties rules on capacity to bind the state.¹⁰⁰ There is no clear classification of which acts are ‘practice’,¹⁰¹ and states often suggest which acts qualify as practice in yearbooks or digests on practice.¹⁰² Indeed, sometimes the ICJ appears to reduce the evidentiary burden for proving customary international law by invoking strong, convincing authorities such as the ILC.¹⁰³ One would imagine that a state would need to bring quite compelling evidence to convince the ICJ to determine that a provision in the Draft Articles on State Responsibility was not customary international law. Beyond these basic conditions, the ICJ and other authorities do not perform any inductive analyses of the secondary rules on the nature and quality of the practice being ‘sufficiently widespread and representative, as well as consistent’.¹⁰⁴ Again, we can note the lack of inductive analysis also on the part of the ILC special rapporteur in reaching his conclusions on these points.¹⁰⁵

After offering competing hypotheses, the ICJ must weigh the evidence. There does not appear to be any inductive analysis on the burden of proof or weight of evidence for customary international law.¹⁰⁶ The ICJ has only issued very vague statements that evidence is weighed and contradicted.¹⁰⁷ The Special Tribunal for Lebanon used the expression ‘beyond any shadow of doubt’ when considering whether a customary rule had been proven, though it did not indicate whether this was the burden of proof it applied or whether this was merely a rhetorical flourish.¹⁰⁸

Having produced a final pool of data on the basis of all of these logical steps, the ICJ will perform an inductive inference to identify the applicable rules (or least says that it will). The usual approach, in line with an inductive logic, is to employ a sampling survey. The actual sampling conducted by the ICJ is not random or following typical scientific approaches for induction.¹⁰⁹ For example, the practice is not simply quantified based on the number of states in alignment, but certain acts by certain states might be weighted more heavily.¹¹⁰ For example, the judges in the Legality of the Threat or Use of Nuclear Weapons advisory opinion disagreed, not about the methodology but about relative significance of the practice.¹¹¹ In both situations, the judges are applying logic to the value of practice.

Some cases will result in insufficient or inconsistent evidence. Talmon has observed that in such cases the ICJ might simply deduce the existence of the rule. He reads the Gulf of Maine case to say that the lack of evidence could lead the ICJ to rely on a deductive approach.¹¹² The present author, however, considers that the chamber in the Gulf of Maine case might have only identified a certain class of norms that are reasonable as to their content and, as a result, imposed a lower burden of proof.¹¹³ That is to say that the determination of the content of the rule preceded the identification of method,¹¹⁴ whereas Talmon reads the chamber judgment as holding that the method of proof came first, and that only when it failed was an alternate method adopted.

Lastly, although it is agreed that, in principle, one applies inductive reasoning to infer the existence of a rule from examples of practice and opinio juris, the precise form of the inference remains somewhat unclear. The inference could be an enumeration of cases and inverse inference, concluding that the frequency of a certain characteristic in the sampled population is the same as in the general population.¹¹⁵ The inference might instead be a predictive inference. This approach attempts to use past examples of actions to predict likely behaviour in the future,¹¹⁶ or uses past practice to identify an underlying characteristic that gives cause to the behaviour and predicts behaviour when that characteristic is present.¹¹⁷ Or, in a similar approach, the investigator could engage in universal (hypothetical) inference, proposing a rule that applies to the general population, due to it being exhibited in the sample pool.¹¹⁸ In the usual adversarial approach, a court practices Bayesian confirmation, where it identifies which of the hypotheses is the better explanation for the evidence,¹¹⁹ though it is certainly possible that a court or other authority could develop its own hypothesis. Some language from the ICJ suggests that it is applying Bayesian confirmation of a universal inference. For example, in examining the evidence in Jurisdictional Immunities case, the ICJ merely observed that practice had not been contradicted with other evidence of practice.¹²⁰ In any event, one cannot use the sample pool merely to describe the likely state practice exhibited and opinio juris held by states; it must identify what custom has been prescribed.¹²¹ These inductive approaches can only result in descriptive outcomes, and one must still make a normative inference from the descriptive outcome.

4 Conclusion

This chapter has analysed the presence of logic and reasoning throughout the ICJ’s approach to customary international law. Logical reasoning takes several forms, primarily deductive or inductive. While the ICJ argues that it applies inductive reasoning, the reality is that at multiple steps in its analysis it also applies deductive reasoning. This approach is clearly apparent when the ICJ assesses the fundamental rules of customary international law, such as the existence and nature of the state practice and opinio juris elements. The ICJ does appear, at least in some cases, to deduce the existence of customary international law as a logical or necessary conclusion from other treaty or customary norms, or by analogy to similar norms, or even perhaps from legal principles. But the ICJ also uses deductive logic when it applies the (primarily) inductive approach. It determines how the elements will be evidenced, evaluated, and weighted.

However, the ICJ is also not very transparent in the logical reasoning it applies. While we might be tempted to conclude that customary international law has no secondary rules at all aside from appeals to deductive logic, the ICJ continues to affirm its adherence to the two-element, inductive approach. A possible solution is to distinguish between the existence and constitution of customary international law from its evidence. And it might also be helpful to observe that the ICJ is, after all, not proving facts, but law, where courts traditionally have more freedom with less demanding standards of evidence. These deductive steps might simply be methods for establishing some fundamental secondary rules but also lowering the threshold for inductive analysis when certain primary rules would make logical sense.

Ultimately, we return to the question posed at the outset of this chapter – that is, whether the identification and interpretation of customary international law is a question of fact or law. If it is a question of law, which seems reasonable, then the ICJ has a much more flexible guide in informing itself of the law, jura novit curia. Talmon concludes that this amounts to an ‘assertion’ of customary international law,¹²² and Hakimi has even argued that there are no secondary rules at all.¹²³ But the analysis of the ICJ discussed above is not completely untethered from the logic of state practice–opinio juris and the various interpretive techniques meant to give content to rules generally. Thus, it is too extreme to say that the ICJ merely asserts rules on the basis of no secondary rules. Instead, it draws on and is constrained by an argumentative framework where it must identify rules with reference to what states do and what they think as a basis, and can give content those rules through deductions and analogies.

6 The Interpretation of ‘Direction or Control’ in Investor–State Arbitration The Case of State-Owned Enterprises

Paula Baldini Miranda da Cruz

1 Introduction

In this chapter I explore how the interpretation of customary international law can be shaped by the underlying premises and political values of a system. My argument focuses on how investor–state arbitration has interpreted the customary international law rule establishing that the actions of state-owned enterprises will be attributed to the controlling state, as expressed in Article 8 of the Articles on the Responsibility of States for Internationally Wrongful Acts (ARSIWA).¹

International lawyers use the term ‘state-owned enterprise’ to refer to corporate entities that are not part of a state but are still owned or controlled by a state. State-owned enterprises pose challenges for international law because, although they are formally independent and autonomous entities, their corporate and operational ties with states can make it hard to distinguish their activities and goals from those of the states that own or control them. This sometimes nebulous relationship between states and state-owned enterprises has generated international concern that states might use state-owned enterprises to cover reprehensible and even illegal activities.²

Without a specific international legal regime for state-owned enterprises, discussions on state involvement in the international activities of these entities should be grounded on general international law, including the customary rules on attribution that are expressed in the ARSIWA. Investment arbitration tribunals have generally agreed on the applicability of customary international law on state responsibility to cases that deal with attribution to states of actions that violate treaty protections.³ However, they have approached these cases from several different perspectives and standards (Section 2). I argue that such variation arises from the specific characteristics of investment law – namely, a cautious approach towards state-owned enterprises, coupled with an individualized application of the ‘effective control’ test. These two elements have pushed tribunals towards interpreting Article 8 of the ARSIWA in an individualized way that calibrates general international law standards in the light of common investment law practices, the rules specifically agreed by the states involved, and the specific needs and circumstances of the parties (Section 3).

2 The Interpretation of Control in International Law and Investment Arbitration

The ARSIWA were developed by the International Law Commission (ILC) as a way of codifying and developing the international law on state responsibility. Although the ARSIWA themselves do not constitute a binding instrument, many of their provisions, including Article 8, are considered to reflect customary international law.⁴ The ARSIWA themselves are rather a subsidiary instrument⁵ that describes these provisions in a way that is considered authoritative. It is worth mentioning here that despite the subsidiary nature of the ARSIWA as a source of international law, the recognized authority of the rules expressed in the ARSIWA has led international lawyers (including myself in this chapter) to broadly refer to these rules as binding.

According to Article 8 of the ARSIWA, the conduct of a non-state actor, including a state-owned enterprise, is attributable to a state if such entity ‘is in fact acting on the instructions of, or under the direction or control of, that State in carrying out the conduct’.⁶ As I describe below, the interpretation of the term ‘control’ has been a subject of discussion in international law. The ILC, in its commentary to the ARSIWA, emphasized that there were different ways of interpreting the term ‘control’.⁷ It is therefore up for those applying Article 8 to determine how to interpret and apply it in light of the circumstances of each case. As noted by the ILC:

It is clear then that a State may, either by specific directions or by exercising control over a group, in effect assume responsibility for their conduct. Each case will depend on its own facts, in particular those concerning the relationship between the instructions given or the direction or control exercised and the specific conduct complained of.⁸

Although the ‘effective control’ test of the International Court of Justice’s (ICJ) is referred to as the standard test for attributing actions of state-controlled entities to states, it has been shaped to different circumstances. Although there are many possible approaches, tribunals have been generally consistent and applied similar tests when faced with similar sets of circumstances (Section 2.1). This effort for consistency contrasts with broader variations in approaches seen in the context of investment tribunals ruling on the attribution to states of the actions of state-owned enterprises (Section 3.2).

2.1 ‘Control’ in International Law

The best-known test for determining whether a state has enough control to be held responsible over the actions of other entities is the ‘effective control’ test set by the ICJ. In all cases where the ICJ has discussed the issue of attribution to states of actions committed by other entities, it has found that states could only be held responsible for the actions of actors that they effectively controlled. In the case of Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. USA), the ICJ established what it considered to be the threshold of control for attribution of conduct to states based on the rule expressed in Article 8. Nicaragua had turned to the Court claiming that the United States was responsible for supporting armed actions by a non-state armed group known as the Contras in Nicaraguan territory. The Court concluded that the United States should be held responsible for supporting the Contras. However, it also found that it could not hold the United States responsible for illegal actions committed by the Contras in their armed operations because, although the United States played a relevant role in the Contras’ operations, it did not have effective control over them.⁹ The ICJ later reiterated its understanding that attribution under Article 8 of the ARSIWA would require evidence that a state has effective control over the actions of a non-state actor in the Armed Activities in the Congo case¹⁰ and in the Bosnia v. Serbia case.¹¹

Other tribunals read the ICJ’s interpretation of control as the standard customary law test for attribution of conduct under Article 8 of the ARSIWA.¹² However, the solution found by the ICJ was not the only possible one. For example, those operating in specialized fields of international law have found that it was sometimes necessary to adopt a lower threshold of control in light of the legal and practical circumstances of the cases they were handling.

This flexibility is illustrated by the International Criminal Tribunal for the Former Yugoslavia (ICTY), which attributed the conduct of armed forces to states by making use of what became known as the ‘overall control’ test. In the Tadić case, the ICTY acknowledged the ‘effective control’ test developed by the ICJ, but found that its high threshold was incompatible with the strict hierarchy under which military operations take form. According to the ICTY: ‘The requirement of international law for the attribution to States of acts performed by private individuals is that the State exercises control over the individuals. The degree of control may, however, vary according to the factual circumstances of each case.’¹³

Following this logic, the ICTY concluded that the ‘effective control’ test set by the ICJ was suited for situations where it was necessary to determine whether the actions of a private individual (or group of individuals) are attributable to a state. In these cases, the ICTY stressed, there must be evidence that such an individual received from a state specific instructions to act as its de facto agent.¹⁴ However, such detailed examination would not be necessary when the state already has authority over an individual or group that operates under an organized hierarchy. Organized and hierarchical structures, such as military units, operate under more predictable, preexisting logics and strategies and therefore do not require a threshold as high as the one expressed by the ICJ in Nicaragua v. USA. The ICTY clarified that:

Normally a member of the group does not act on his own but conforms to the standards prevailing in the group and is subject to the authority of the head of the group. Consequently, for the attribution to a State of acts of these groups it is sufficient to require that the group as a whole be under the overall control of the State.¹⁵

The ICJ responded specifically to the Tadić test in its Bosnia v. Serbia judgment, suggesting that the approach taken by the ICTY in this case was ‘unpersuasive’ and dismissing the possibility of applying it in the context of state responsibility.¹⁶ The ICTY, however, kept following its own test as set in Tadić,¹⁷ with defenders of this approach arguing that both tests can coexist because they are designed to deal with different circumstances.¹⁸

The peculiarities of state-owned enterprises may also justify a specific approach to establish that a state controls them. In its commentary to Article 8 of the ARSIWA, the ILC discussed the attribution of conduct of enterprises that are owned and controlled by the state as an example of a situation that could warrant a threshold different from that used in ICJ case law. According to the ILC, the conduct of a state-owned enterprise should be attributed to the state pursuant to Article 8 of the ARSIWA when there is ‘evidence … that the State was using its ownership interest in or control over a corporation specifically in order to achieve a particular result’.¹⁹

The ILC’s commentary relied on an example from the case law of the Iran–US Claims Tribunal (IUSCT) on the attribution of the conduct of state-owned enterprises. The IUSCT, a tribunal created as part of a set of measures to manage the political crisis between the United States and Iran arising from the 1979 hostage crisis and the subsequent freezing of Iranian assets by the United States, decided several cases that involved the attribution to the state of the actions of state-owned enterprises. These decisions were grounded on interpretation of Article VII(3) and (4) of the Claims Settlement Agreement, which provided for the attribution to Iran and the United States respectively of the acts of the entities they controlled.

In most cases, the IUSCT attributed the actions of state-owned enterprises to the state only if there was proof that the latter was using its controlling stake to direct the actions of the enterprise.²⁰ However, in cases such as Foremost Tehran v. Iran the tribunal’s decision on attribution rested on the corporate characteristics of an enterprise – namely, ‘the identity of its shareholders and the composition and behaviour of its board of directors, which must be examined together’,²¹ rather than on the specific interactions between the state and the corporations.²² The reason for such variation was the position taken by the minority of judges, as stated in Judge Khalilian’s opinion in the case of SEDCO v. Iran:

Until now, the majority has taken the position, in its past Awards, that the term ‘control’ in Article VII (paras. 2, 3, 4) involves a qualitative predominance and, in the words of Chamber Three, ‘control over management’. … Nonetheless, it is worth noting, as a digression, that this same Tribunal has elsewhere correctly given the meaning of ‘control’ as set forth in paragraph 3, since it has held that two conditions must be met, before there can be a finding of control.²³

The ILC, when examining the IUSCT case law, focused on the majority cases where the tribunal looked for evidence that the state had used its corporate power to push the state-owned enterprise towards adopting specific actions.²⁴ The ILC found these majority cases representative, not only of the IUSCT practice for dealing with state-owned enterprises but of the position of international law in general.²⁵

These examples show how there are multiple ways of interpreting and applying Article 8 of the ARSIWA. The term ‘control’, in the way that it is used in the ARSIWA, or even the ‘effective control’ terminology used by the ICJ, are polysemic terms – they do not encompass a single type of relationship between states and non-state entities. It is up to those applying Article 8 to examine whether each situation they face meets the conditions for attribution under that provision. However, this case-by-case approach does not mean that Article 8 should be interpreted indiscriminately or inconsistently. In fact, all bodies examined in this section have sought a consistent application of Article 8 when dealing with similar sets of facts. Consistency in these cases is achieved not by applying the exact same text, but rather through constant judicial dialogue. This logic can be seen in the intense dialogue between ICJ and the ICTY about whether there should be a single control test, and if so, which should be the correct one. Both concluded that there were different possible interpretations for the term ‘control’ and that the test that each of them had been applying so far was the correct one for the specific circumstances they were facing.²⁶ Similarly, in the IUSCT the judges that were in the minority in cases such as SEDCO engaged in internal judicial dialogue when dissenting from its own case law.²⁷

2.1.1 Control Tests in Investment Arbitration

Investment tribunals have followed a tendency similar to that of their counterparts in other fields of international law. However, there is a key difference between the bodies examined in Section 2.1 and investment arbitration tribunals. Unlike the former which are permanent institutions with a stable composition of judges, investment arbitration is a fragmented dispute settlement system. Although investment arbitration is developed on the basis of common principles and goals, cases are grounded on agreements that are negotiated and drafted individually, each with its own particularities. Neither these agreements nor the tribunals that settle the disputes arising from them have formal ties with each other. There is also no formal obligation to follow precedent, meaning that tribunals may rely on previous case law when appropriate, but are not forced to follow it.²⁸ As a result, the findings made by a tribunal in one case do not bind other tribunals, making it hard to make definitive affirmations about the field.

With that caveat made, investment tribunals have generally acknowledged the ICJ’s ‘effective control’ test as the standard approach for holding states responsible for the actions of non-state actors. In the case of Marfin v. Cyprus, for example, the tribunal stressed that investment arbitration jurisprudence had consistently upheld the ICJ test and that there was no reason to depart from it.²⁹ As a consequence, the tribunal found that Cyprus could not be held responsible for treaty violations allegedly committed by a private bank, because although Cyprus had sometimes interfered in the bank’s administration and guided some of its decisions, there was no evidence that Cyprus had effective control over the bank’s alleged violations.³⁰

Arbitral tribunals’ attitudes towards the ICJ test vary, however, when the cases concern state responsibility for the actions of a state-owned enterprise. While many cases have followed the ICJ’s threshold of effective control, others have adopted much lower standards. Cases can be divided into three groups:

1. 1. those applying the ‘effective control’ standard set by the ICJ;

2. 2. those that consider the ‘effective control’ standard too high for cases involving state-owned enterprises and instead determine that states that cleared or authorized an action by a state-owned enterprise are responsible for those actions; and

3. 3. those that presume that states are responsible for the actions of any enterprise in which they hold more than 50 percent of the shares.

Cases applying the ICJ’s ‘effective control’ standard include Jan de Nul v. Egypt, where the tribunal examined whether actions of an Egyptian agency with distinct legal personality were attributable to the state of Egypt. The tribunal focused strictly on international rules on attribution and followed general standards for the interpretation of ARSIWA Articles 4, 5, and 8,³¹ making specific reference to the ICJ’s effective control test.³² Such an approach was also followed by the tribunals in Hamester v. Ghana, White Industries v. India, and Tulip Real Estate v. Turkey.³³

In several other cases the tribunals adopted much lower thresholds of control. In the Bayindir v. Pakistan case, the tribunal had to determine whether Pakistan should be held responsible for clearing actions of the National Highway Authority (NHA) that violated investment protections owed to the claimant. The tribunal was aware that state clearance met neither of the thresholds set in the ICJ’s effective control test and the ICTY’s overall control test, but chose nevertheless to attribute the NHA’s conduct to Pakistan under Article 8 of the ARSIWA.³⁴ The tribunal summarized its logic in the following way:

[T]he Tribunal is aware that the levels of control required for a finding of attribution under Article 8 in other factual contexts, such as foreign armed intervention or international criminal responsibility, may be different. It believes, however, that the approach developed in such areas of international law is not always adapted to the realities of international economic law and that they should not prevent a finding of attribution if the specific facts of an investment dispute so warrant.³⁵

The tribunal unfortunately did not go further into clarifying what were the ‘specific facts of the investment dispute’ that justified its departure from tests that were already established in international case law. Nevertheless, such interpretation was later followed by the tribunal in Deutsche Bank v. Sri Lanka. In this case, the tribunal found that the actions of a state-owned entity should be attributed to Sri Lanka on the basis of evidence that the entity was following a governmental directive when it started the program that led to the dispute.³⁶

Most tribunals are not, however, so explicit on the reasons that led them to depart from the general ‘effective control’ test. Take, for example, the case of Maffezini v. Spain. The question that was raised before the tribunal concerned the attribution to the state of the actions of SODIGA, a state-owned company engaged in a joint venture with the claimant. In its analysis, the tribunal stressed that the applicable law to determine attribution was that of state responsibility, in particular the provisions contained in the (then) draft ARSIWA. However, its analysis followed very different lines from those in the ARSIWA or those used by other international law courts. The tribunal ruled that the actions of state-owned entities are presumed to be attributable to the state if that entity (1) was owned by the state, (2) was controlled by the state, or (3) performed state functions.³⁷ The tribunal then focused on what it described as a ‘structural test’, through which the tribunal allowed itself to presume that any entity in which the government owned more than half of the shares would be operating under its control. Based on this test, the tribunal concluded that the Spanish state was responsible for SODIGA’s actions because it owned ‘no less than’ 51 percent of its shares.³⁸

The tribunals in RFCC v. Morocco and Salini v. Morocco approached ‘control’ in Article 8 from a similar perspective. Both cases arose from contracts between foreign investors and the Société Nationale des Autoroutes du Maroc (ADM), a state-owned enterprise responsible for many of Morocco’s highways. In RFCC v. Morocco, the tribunal concluded that Morocco had control over ADM after examining the information on its corporate ownership and its administration contained in its bylaws.³⁹ In Salini v. Morocco, the tribunal went further with its suggestion of attributing to states the actions of all state-owned enterprises, which the tribunal defined as ‘any commercial company dominated or predominantly controlled by the State or by State institutions, whether it has a legal personality or not’.⁴⁰ Years later, this approach was reiterated in the case of Helnan v. Egypt, where the tribunal attributed the actions of a corporation to Egypt based solely on the fact that it was owned by Egypt.⁴¹

In some cases, tribunals have also combined elements from different interpretations, tailoring their analysis of control to the circumstances of the case. In the case of Karkey Karadeniz v. Pakistan, the tribunal applied a test that included both corporate and effective control when applying Article 8 of the ARSIWA. The case concerned contracts signed by the claimant with a Pakistani corporation as part of a broader governmental plan to tackle the Pakistani energy crisis. The tribunal started its examination by pointing out that the company itself had acknowledged that it was ‘owned and controlled by the government of Pakistan’, suggesting that it would apply the criterion of corporate control to the ‘control’ threshold in Article 8 of the ARSIWA.⁴² However, the tribunal then stressed that the evidence on record indicated that it was the government of Pakistan that had negotiated the contract and selected the corporation that was going to enter into it as a buyer.⁴³ Ultimately the tribunal’s conclusion was that the company’s ‘acts related to the conclusion and execution of the Contract were directed, instructed or controlled by Pakistan, and are accordingly attributable to Pakistan, irrespective of the disclaimer contained in the RFP [Request for Proposal]’.⁴⁴

The interpretation of the term ‘control’ in Article 8 of the ARSIWA will therefore vary depending on the specific circumstances of a case, the broader legal framework, and the rules which the tribunal is applying to the case. In this sense, investment arbitration tribunals dealing with questions of attribution of conduct of state-owned enterprises to states have followed similar patterns to the ones seen in other international law contexts. The use of the ‘effective control’ test by the ICJ in preference to a lower standard is a way to prevent it from overstepping its functions and ensuring that it does not meddle in states’ domestic affairs. On the other hand, the ICTY employed a lower threshold justified by the fact that armed troops operate under the oversight of the state and follow a rigid hierarchy.

However, as shown by the IUSCT, the particularities of state-owned enterprises may warrant for a specific interpretation of the term ‘control’. The control test applied by the majority of the IUSCT determined, first, whether the state was able to use its shares or other corporate or institutional mechanisms to control the actions of the enterprise. Secondly, the tribunal would look at whether the state had indeed used those powers to control the enterprise and have it perform the specific actions discussed in the case at hand. In investment law, tribunals applying Article 8 of the ARSIWA have employed three different tests, holding states responsible (1) only for the actions of state-owned enterprises they effectively controlled and specifically directed, adopting a test similar to that of the IUSCT; (ii) for any action they authorized; or (iii) for any action of the state-owned enterprises over which they held corporate control.

3 Investment Law Shaping the Concept of Control

In the absence of specific provisions on state responsibility for the actions of state-owned enterprises, the applicable rules are those contained in the ARSIWA, which is deemed to mostly reflect customary international law. However, the interpretation of such rules is shaped by the specific factual and legal context of each case. The factual context relates to the particularities of the relationship between the state and the entity, including the powers that the state holds as a shareholder and the specific interactions between the state and the enterprise in the circumstances of the case. The legal context comprises the characteristics of the field of international law and the instruments applicable to the relationship between the parties, including the legal principles that guide them, and how the stakeholders see and apply the rules contained in these instruments.⁴⁵

In this section, I discuss two particularities of international investment law that may help explain why arbitrators adopt lower thresholds of control when applying Article 8 of the ARSIWA to the actions of state-owned enterprises. International investment law is a field that is largely inspired by the goal of depoliticizing investment relations, which translates into discouraging states from participating directly in investments.⁴⁶ This underlying goal may push arbitrators to approach state-led investment initiatives cautiously (Section 3.1). On top of that, arbitrators have in other situations equated ‘effective control’ with corporate control, thus suggesting that investment tribunals interpret Article 8 of the ARSIWA much more flexibly than courts that operate in other fields of international law (Section 3.2). Ultimately, a tribunal will calibrate the threshold of the control by looking at the characteristics of the field, general international law standards, and the particularities of each case (Section 3.3).

3.1 Caution towards State-Led Initiatives in the Development of International Investment Law and Investment Arbitration

Investment arbitration is often guided by a general cautiousness towards state-led initiatives. International investment law was developed around the principle of investment neutrality, which assumes that state involvement in investment relations may generate political risks that harm foreign investment.⁴⁷ The term ‘political risk’ is not defined legally but is used in investment and business circles to refer to risks associated with political fluctuations such as changes of power and policy. Many of the protections contained in investment agreements are aimed at reducing political risks that foreign investors may face in the host state – for example, most-favored-nation and fair-and-equitable-treatment clauses. Most-favored-nation clauses prevent the host states’ relationships with other states from interfering with investment relations by allowing foreign investors to claim most-favored-nation treatment.⁴⁸ Fair-and-equitable-treatment provisions require foreign investors to be treated ‘fairly and equitably’⁴⁹ – terms that have been interpreted as a blanket protection for foreign investors against host state actions that seem to be politically motivated or ‘irrational’.⁵⁰

This logic of limiting state power also applies to investment arbitration. Investors often feel that the host states’ domestic courts – the default forum for them to settle these disputes – may be biased against foreign investors or lack the expertise to deal with investment treaty claims. Even before clauses providing for arbitration as a means to settle disputes started to be introduced in investment treaties, states and investors were already reaching out to organizations such as the World Bank to request informal assistance to settle their disputes.⁵¹ At the same time, the international dispute settlement options that existed then were limited and politically sensitive. To start a case against the host state, investors had to convince their home states to exercise diplomatic protection. This forced investors to spend significant time and political resources without any guarantee that the case would be picked up by their home states or lead to a desirable outcome.⁵² Investment arbitration as a mechanism of dispute settlement that investors can use directly, without having to appeal to their state of origin, was thus considered a more politically neutral option than both domestic dispute settlement and diplomatic protection.⁵³

In addition to depoliticizing the access of investors to international dispute settlement mechanisms, there is also the goal of depoliticizing the resolution of disputes themselves. Investment law often deals with subjects that are highly sensitive to states,⁵⁴ and one of the central goals of investment arbitration is to reduce state influence over litigation outcomes.⁵⁵ This includes, for example, prohibiting investors’ home states from directly engaging in investment disputes, as provided in Article 27 of the ICSID Convention.⁵⁶

The ICSID Convention also prevents states from making use of investment arbitration as investors themselves. The idea of having investor-states as parties to investment arbitration was raised and rejected during the negotiations of the ICSID Convention. Many of the states involved in negotiations feared that allowing states to access investment arbitration as investors would facilitate political capture of the system, which would defeat the purpose of creating a depoliticized system.⁵⁷ Article 25(1) of the ICSID Convention, which establishes ICSID jurisdiction, therefore excludes the possibility of interstate disputes:

The jurisdiction of the Centre shall extend to any legal dispute arising directly out of an investment, between a Contracting State (or any constituent subdivision or agency of a Contracting State designated to the Centre by that State) and a national of another Contracting State …

Similarly, the early development of investment arbitration seems to have embedded in its discussions the idea that, although formally separate from states, state-owned enterprises would probably not be eligible claimants in investment arbitration because they operated under state control. Early ICSID drafts determined that, for jurisdictional purposes, state-owned enterprises should be equated to states.⁵⁸ The final draft of the ICSID Convention also allowed states to consent to foreign investors filing claims directly against their state-owned enterprises, therefore presuming that those enterprises were part of host states themselves.⁵⁹ Even today, there are investment treaties with provisions limiting the protections afforded to state-owned investors and, as a consequence, their capacity to resort to investment arbitration.⁶⁰

However, the creators of this dispute settlement system were aware that these preconceptions were subjective and could not reasonably justify a blanket prohibition against state-owned claimants making use of investment arbitration. When faced with the question of whether state-owned enterprises should be excluded from filing investment arbitration cases, Aaron Broches, former general counsel of the World Bank and one of the main sponsors of the ICSID Convention, acknowledged that they could play distinct roles in an economy, but seemed to believe that truly independent and market-oriented state-owned enterprises were an exception. In Broches’s words, ‘[t]here would appear to be no reason why a state-owned enterprise, if it elected to assimilate itself to a private enterprise rather than a government agency’⁶¹ should be treated differently from a privately owned corporation.

Most of the discussions on state-owned enterprises in investment law were, however, informal and were not translated into explicit treaty provisions. Broches’s writings on the ICSID negotiations indicate that the drafters of these treaties may have thought that it was not necessary to add such a level of detail on state-owned enterprises, since they shared a ‘common understanding’ on the subject. This understanding was that although state-owned enterprises could not be automatically equated to states, most of them presented a risk for a free market economy because they operated under strict state supervision. This notion, however, covered only the political behaviour and characteristics of state-owned enterprises.

It is worth noting that this tendency to overgeneralize treaty terms on state-owned enterprises also prevails in modern investment treaties. With the exception of the EU–China Comprehensive Agreement on Investment, which specifically lists the entities covered by its provisions,⁶² the few treaties that contain provisions on how to distinguish state-owned from other corporations or from states still do so in very broad terms, such as ‘when it exercises any regulatory, administrative or other governmental authority’.⁶³

While the legal instruments shaping international investment law do not provide much guidance on how to deal with legal questions involving state-owned enterprises, they show that stakeholders engaged in developing international investment law and investment arbitration were cautious towards recognizing rights of state-owned enterprises as investors. As stressed by the tribunal in Maffezini v. Spain, the overall framework of international investment law presumes that state-owned enterprises will, as a general rule, operate alongside states and even as part of their structure.⁶⁴ In the extreme, relying on such notions may lead to decisions such as the one taken by the tribunal in Bayindir v. Pakistan, which concluded that it could attribute to a state the actions of any enterprise that it owns, regardless of there being specific evidence showing that the state indeed exercised control over that entity.⁶⁵

3.2 Using ‘Effective Control’ as a Flexible Standard

A second element shaping how investment arbitration approaches the attribution to states of state-owned enterprise actions is the flexibility with which investment tribunals have approached the term ‘effective control’. Tribunals have relied on the terminology of effective control in various contexts and referring to different thresholds of control, including corporate control. In the context of investment arbitration, the term ‘effective control’ has been used to indicate that a tribunal must look at the facts of each case, rather than relying on general formulas that presume control.

The legal issue with regard to which the tribunals show the greatest flexibility in the interpretation of the standards of effective control is the determination of the nationality of foreign investors. As stated in Article 25(1) of the ICSID Convention, modern investment arbitration is supposed to be between a state and a national of another state. Therefore, a corporate foreign investor will be allowed to file an investment claim on its own only if it proves that it is a national of a state party to a relevant treaty. However, it is not easy to determine the nationality of an investor, since many host states require investments to be made through local subsidiaries that would not normally qualify as foreign investors. In general international law, the nationality of a corporate investor is determined on the basis of its place of incorporation,⁶⁶ which makes it impossible for foreign shareholders to file claims seeking relief for damages suffered through a local subsidiary. Aware that this would hamper the access of transnational companies to investment arbitration,⁶⁷ the drafters of the ICSID Convention included in Article 25(2)(b) the possibility for states to agree to treating local subsidiaries controlled by foreign corporations as foreign nationals:

(2) ‘National of another Contracting State’ means: …

(b) any juridical person which had the nationality of a Contracting State other than the State party to the dispute on the date on which the parties consented to submit such dispute to conciliation or arbitration and any juridical person which had the nationality of the Contracting State party to the dispute on that date and which, because of foreign control, the parties have agreed should be treated as a national of another Contracting State for the purposes of this Convention.⁶⁸

Many investment treaties thus include in their dispute settlement chapters provisions that also treat as foreign investors subsidiaries that are controlled by a national of a foreign state.⁶⁹ However, such provisions require proof that the claimant parent company has corporate control over the local subsidiary.⁷⁰ Although the most obvious form of corporate control would be to hold more than half of the subsidiary’s shares, there are many ways of controlling a corporation – for example, through special voting rights, golden shares, or joint ownership, to name but a few. Perhaps to avoid being blindsided by looking only at majority shareholding, tribunals have treated as nationals of a state claimants that are under the ‘effective’ corporate control of an entity established in that state.⁷¹

Despite the use of terminology identical that used by the ICJ in the Nicaragua v. United States case, the test used by arbitral tribunals to determine the nationality of investors could not be more different from the one employed by the ICJ. Whereas the ICJ test focused on whether a state had de facto control over another entity’s specific actions, the test used by arbitral tribunals to determine the nationality of investors involves an inquiry into the company’s corporate control mechanisms. In the case of Rompetrol v. Romania, the tribunal examined the successive changes in the ownership of Rompetrol since 1993 to determine who had ‘effective control of the corporate entities in question’.⁷² The Vivendi I annulment committee adopted a similar approach to examine whether a transfer of control over one of the claimants could affect its nationality, stressing that a company could be considered a foreign national only if it was ‘effectively controlled, directly or indirectly, by nationals of one of the contracting parties’.⁷³

Neither of the tribunals in the cases of Rompetrol or Vivendi I referred or drew connections to Nicaragua v. United States or to Article 8 of the ARSIWA. This raises the question of whether these two investment tribunals had the intention to apply and interpret the ICJ’s effective control test through the lens of investment law when adopting such terminology. Nevertheless, the use of the term ‘effective control’ has led other tribunals to treat such case law as part of a common analytical framework. In Pan American Energy and BP Argentina v. Argentina, the claimants and the tribunal referred to case law on the determination of nationality and on attribution of conduct to justify the use of corporate control as a criterion to determine nationality.⁷⁴ The resulting award thus combined the case law on ‘effective control’, thereby creating another new test for attribution of conduct under these criteria.⁷⁵

Investment tribunals therefore approach the interpretation of the term ‘control’ under Article 8 of the ARSIWA from a rather unique perspective. In the absence of a distinction between ‘corporate nationality control’ and ‘control over non-state actor’s conduct’, the concept of ‘effective control’ ceases to be a specific threshold for control in the context of investment arbitration. Rather than using it as a reference to a threshold of control, investment tribunals seem to treat the ‘effective control’ standard as translating an obligation to examine each case individually and to evaluate different legal approaches to reach a solution that is appropriate to the specific circumstances of the case.

3.3 Judicial Reasoning as a Compass for Determining a Threshold for Control

The flexibility with which tribunals have approached the ‘effective control test’ is not exceptional in investment arbitration. As argued elsewhere, investment arbitration tribunals approach situations on a case-by-case basis, tailoring their legal solutions to the characteristics of the agreements at hand and the specific needs of the parties to the dispute.⁷⁶ Faced with the question of attribution of state-owned enterprise conduct to states based on Article 8 of the ARSIWA, investment tribunals will therefore determine what threshold of control to apply in each case by calibrating⁷⁷ standards used in general international law and the specific characteristics of the international investment law applicable to the case at hand.

An examination of the way in which investment arbitration tribunals applied Article 8 of the ARSIWA raises the question not only of the threshold of control that they apply but even more so the elements that they take into consideration to determine the threshold of control applicable to each case. A tribunal that rules on whether to attribute the actions of a state-owned enterprise to a state pursuant to Article 8 of the ARSIWA will have to consider whether the (very high) threshold of control set by the ICJ is appropriate to the circumstances of the case at hand,⁷⁸ including the rules agreed upon by the treaty parties; the common practices in the field;⁷⁹ the treaty parties’ laws on state-owned enterprises;⁸⁰ and evidence of the involvement of the treaty party in the state-owned enterprise or in events related to the case.⁸¹

The highest threshold of control that a tribunal could adopt would be the one applied by the ICJ in the Nicaragua v. United States case, which holds states responsible only for actions that they have specifically controlled by, for example, ordering or directing the state-owned enterprise to act in such a way. The lowest threshold would be to attribute to the state the actions of any entity in respect of which it has participatory decision-making power, regardless of whether it is indeed involved in the decisions taken concerning that entity. Between these two extremes there is a range of other possible thresholds that may be adopted depending on the context of a case. A tribunal may, for example, hold states responsible for the actions of non-state entities when they have evidence that the state formally cleared or authorized those actions. All of these approaches are in principle allowed by international investment law and investment arbitration, as arbitral tribunals have the power to interpret and apply international law to solve the conflict they have at hand.

Tribunals’ powers to interpret and apply open-ended rules such as the one expressed in Article 8 of the ARSIWA is tied to an obligation to provide reasoning. Article 48(3) of the ICSID Convention requires tribunals to state the reasons upon which they have made their decisions. Article 34(3) of the UNCITRAL Arbitration Rules contains a similar obligation, which applies unless the parties have agreed otherwise. In ICSID proceedings, an arbitral award that lacks an account of the tribunal’s reasoning may even be annulled pursuant to Article 52(1)(e) of the ICSID Convention. The amount of detail that a tribunal must give to fulfill its obligation to provide its reasoning will vary from case to case. As noted by the annulment committee in Wena, there is no single compulsory format in which the tribunal must present its reasons, and it can even leave its reasons implicit, ‘provided that they can be reasonably inferred from the terms used in the decision’.⁸² For example, we can assume that a tribunal dealing with Article 8 of the ARSIWA that applies the exact same threshold for control as the ICJ did in Nicaragua did so because it saw no specific reason to recalibrate the general international law standard. However, if a tribunal issues a decision that seems to depart from previous understandings, it should consider explaining why it decided to do so.⁸³

Although tribunals enjoy considerable freedom when interpreting open-ended rules such as that expressed in Article 8, references to different approaches in a single award suggest that, in investment arbitration, the term ‘effective control’ refers more to a standard of evaluation than a specific threshold of control.⁸⁴ Take the tribunal in Karkey Karadeniz, for instance, which justified its decision on attribution on the basis of elements that refer to corporate control, de facto control, and specific instructions – namely (1) the state-owned had acknowledged that it was owned and controlled by the government of Pakistan; (2) the government of Pakistan had approved the contract related to the dispute; (3) the government of Pakistan was the guarantor of that contract; and (4) the buyer was not allowed to interfere in licenses granted in the contract, which was interpreted as a sign of bad faith.⁸⁵ The diverse interpretations, each unique to a particular award, demonstrate the elasticity the term ‘effective control’ has within this system.

In the absence of a specific threshold of control to be applied uniformly across cases, a correct application of Article 8 of the ARSIWA relies on judicial reasoning. Rather than simply looking at the case law for possible tests and picking one, investment arbitration tribunals must explain their reasons when ruling on what would be the correct threshold of control to be applied in the case before them. As tribunals are not limited in the reasoning that they need to present to justify their decision, they have the power and freedom to decide what elements they will consider relevant in each case and how they weigh each of those elements. However, those reasons must be clear and rational from the stance of international investment law.

4 Conclusion

Although the ICJ’s effective control test is commonly described as a standard solution for applying Article 8 of the ARSIWA, the ICJ has itself recognized that this test cannot be applied universally.⁸⁶ Being a polysemic term, ‘control’ in Article 8 can only be interpreted in the light of the circumstances of a particular case. As a consequence, tribunals applying Article 8 have each had to develop their own control tests according to the legal and factual particularities of the cases before them. The process of interpreting these tests required tribunals to dialogue with each other in order to determine what elements it was appropriate for them to rely on when interpreting control in the cases before them.

Investment tribunals have often interpreted Article 8 of the ARSIWA differently in each case. Rather than establishing a single threshold that would be applied in every case involving state-owned enterprises, arbitral tribunals gauge the ideal threshold of control on the basis of the characteristics and needs of each case. Each tribunal operates independently and therefore has the power to decide alone what factors it will take into consideration when it determines the level of control, such as (1) the importance of following general international law precedent; (2) the specific characteristics of the case at hand, including the parties’ needs and the particularities of the treaty that they agreed upon; and (3) the legal principles that guide international investment law and common practices in investment arbitration. In this chapter, I have focused on the last of these elements and identified two characteristics of international investment law that play a relevant role in tribunals’ interpretations of Article 8 of the ARSIWA in cases involving state-owned enterprises.

The first of these characteristics is the principle of investment neutrality that inspires international investment law and guides investment agreements. The principle of investment neutrality assumes that state participation or interference in investment relations may create political risks prejudicial to investment relations, and acts as a warning to stakeholders to approach any state-led initiative with caution. In practice, this caution guides the drafting of treaty provisions focusing on the protection of foreign investment and may lead tribunals to interpret provisions in ways that extend the scope of state liability for participating directly in foreign investment. The second characteristic is the fact that investment tribunals have used the term ‘effective control’ to refer to other levels of control besides the very high and stable threshold set by the ICJ in Nicaragua v. United States. This flexible approach towards effective control suggests that investment tribunals approach cases from a more individualized perspective and one that takes into consideration the principles that guide the field.

However, this individualized approach towards the application of Article 8 of the ARSIWA increases the burden laid upon tribunals to justify their decisions. Tribunals have the obligation to provide in their awards the reasons that led them to decide in a certain way. While there is no specific format for presenting these reasons, they must be clear to the reader and follow a rational line of thought. When calibrating the threshold of control that they are going to apply in each case, tribunals must therefore clarify what elements they considered relevant for such calibration, how they have weighted them, and why they concluded that the threshold applied is best suited for that specific case.

7 The Court of Justice of the EU and CIL Interpretation Close Encounters of a Third Kind?

Tamás Molnár *

the intellectual prison of custom seems to be gradually transformed into a large dance floor where (almost) every step and movement is allowed

Jean d’Aspremont, ‘Customary International Law as a Dance Floor: Part I’ (EJIL:Talk! 14 April 2014)

1 Setting the Scene

It is uncontested that the European Union (EU) – endowed with distinct international legal personality (pursuant to Article 47 of the Treaty on European Union (TEU)) and being a subject of international law – is bound by relevant norms of customary international law (CIL).¹ Rules of CIL form an integral part of the EU legal order, and the Court of Justice of the EU (CJEU) must use CIL at least as an interpretive tool.² The status of CIL within EU law does not differ from that of international agreements which are binding on the EU,³ as a result of which rules of universal CIL likewise prevail over conflicting secondary EU law.

As an international legal entity and an international actor, the EU can exert formative influence on the development of CIL rules, including through interpreting them. As Advocate General Szpunar pointed out, ‘so far as customary international law concerns questions pertaining to matters falling within the mandate of international organisations, the practice of international organisations may also contribute to the formation or expression of rules of customary international law’.⁴ He also expressed the need for CIL rules in principle – putting aside regional⁵ and bilateral⁶ custom – to be consistent globally and contain no notable contradictions.⁷

Still, the CJEU’s interpretations of CIL norms and the interpretative methods and techniques it employs have received little attention in legal scholarship.⁸ Indeed, critical analysis of the interpretation of CIL rules by international courts and tribunals has in general suffered similar neglect – not to mention the United Nations (UN) International Law Commission’s awkwardness in addressing this matter in its Draft Conclusions on Identification of Customary International Law⁹ – even though the questions of both interpretation and customary law are classic topics in international law scholarship.¹⁰

The CJEU, including its Advocates General, generally finds and identifies rules of CIL in (codification) treaties to which the EU is not a party¹¹ and/or accepts them as customary norms on the basis of judgments of the International Court of Justice (ICJ)¹² and its predecessor, the Permanent Court of International Justice (PCIJ),¹³ using the ICJ/PCIJ rulings as a short route for establishing the existence of a CIL rule.¹⁴ But is interpretation needed, then? Put differently, once a CIL norm has been identified, does its content become known? This is where the need for interpretation of such unwritten norms emerges. According to the CJEU, ‘interpretation … clarifies and defines where necessary the meaning and scope of [a] rule as it must be or ought to have been understood and applied from the time of its coming into force’.¹⁵ In interpretation generally, the CJEU has shown a preference for certain methods – namely, systemic, teleological, and dynamic interpretation – with a view to attaining the objectives of the European integration project as defined by the autonomous EU legal order. As part of EU law, CIL is, in principle, also subject to the same interpretive methods and practices.

This chapter aims to map and understand the ways in which the CJEU interprets CIL rules using its aforementioned toolbox and compares them to those that exist for the interpretation of treaties under the Vienna Convention on the Law of Treaties (VCLT). First, however, the CJEU’s engagement with CIL in general (Section 2) and its general methods interpreting EU law (Section 3.1) will be briefly considered. Then, through a thorough review of relevant case law in Section 3.2, the core of this study, the chapter will seek to reveal what reasons lie behind the CJEU’s particular approach, its interpretative choices, and its deviations from mainstream techniques, if any. The enquiry is guided by the following questions: does the CJEU’s engagement with CIL interpretation display features that are unique to it? If so, what are they and to what extent is this the case? What factors influence the CJEU’s preference for using diverse methods of interpretation of CIL? Is such uniqueness or lack of coherence likely to further fragment international law? And does it strengthen or weaken the authority of the EU Court as an influential judicial actor in this regard. Lastly, Section 4 will critically assess the specificities and challenges of CIL interpretation by the CJEU against the backdrop of the EU as a quasi self-contained regime and the sui generis nature of its legal order, its specific integration objectives, and the particularity of the judicial function the CJEU performs.

2 Assessing the Landscape: The CJEU’s Engagement with CIL in General

At first sight, among the various sources of public international law codified in Article 38 of the ICJ Statute,¹⁶ and even beyond that,¹⁷ CIL seems to have limited importance from the perspective of EU law, particularly compared to written sources of international law, notably treaties and decisions of international organisations. Yet, it is not ill-founded to argue that CIL rules play a more important role in the EU legal order than in the domestic legal systems of EU member states. The reason for this is that, unlike most states, the EU as a distinct international legal person could not or did not accede to a great number of international conventions that codify certain areas of (customary) international law.¹⁸ As a consequence of therefore not being bound by codified treaty rules, the EU remains bound by parallel existing CIL norms,¹⁹ which have to be applied by the CJEU when confronted with issues of international law in individual cases. Illustrative in this regard is the 1969 VCLT²⁰: the CJEU regularly invokes its provisions and relies on its rules as written manifestations of identical CIL rules existing beyond the text itself.²¹

CIL is one of the classic sources of international law, and some of the key rules of the international legal order continue to exist in this unwritten, non-codified form.²² There are too many to name here; suffice it to say that they can be found in ample numbers in the fields of diplomatic law, state responsibility, treaty law, international refugee law, international human rights law and international criminal law, for example.

CIL rules that have been recognised as part of the EU legal order in CJEU jurisprudence include the right of individuals to enter their own country;²³ the right to innocent passage and freedom of navigation under the law of the sea;²⁴ certain principles of the law of treaties (e.g. rules of treaty interpretation, the relative effect of treaties, their territorial scope);²⁵ the jurisdictional immunity of states;²⁶ the status and immunities of heads of state;²⁷ the right of self-determination and peoples’ permanent sovereignty over their natural resources;²⁸ states’ total and exclusive jurisdiction over their airspace; and the freedom to fly over the high seas²⁹ – and the list continues.³⁰

The CJEU employs CIL first and foremost as an interpretative tool when dealing with the acts of EU institutions – for instance, when elucidating the meaning and content of such acts in preliminary ruling proceedings³¹ in the light of international law binding upon the Union. Also, CIL has often been used by the CJEU to delimit the material scope and the boundaries of EU law, including the EU treaties.³² This dynamic process of jointly – and, preferably, harmoniously – applying legal norms of different types and origins necessarily includes the interpretation of CIL rules, too. In theory, CIL can also serve as a ground on which to assess the legality of secondary EU law whose validity has been challenged. However, when private parties seek to invoke customary norms before the CJEU as a standard for reviewing of the legality of a given piece of EU legislation, it must be checked whether the CIL norm at hand is generally accepted; is capable of calling into question the competence of the EU to adopt secondary legislation; and can affect the rights that individuals derive from EU law or creates obligations under EU law in their regard.³³ Given that, in the words of the CJEU, ‘a principle of customary international law does not have the same degree of precision as a provision of an international agreement’,³⁴ CIL can thus generally be invoked as a ground to invalidate conflicting EU secondary legislation only in limited circumstances.³⁵ Given the less precise contours of customary norms, the CJEU has held that the judicial review of a piece of EU secondary legislation in the light of CIL must be limited to the question of whether, in adopting the legal act, the EU institutions made manifest errors of assessment concerning the conditions for applying such a CIL norm.³⁶

3 The CJEU and the Interpretation of CIL: A Peculiar Path

Let us start with a baffling, but basic, preliminary question: why is interpretation – understood as attaching meaning to or elucidating meaning – needed in law? It has become a truism that legal notions have an ‘open texture’ (to use Hart’s words³⁷), manifesting themselves in some grey zone beyond the ‘core of settled meaning’ of a given norm.³⁸ Interpretation, which is inherent in any adjudicative exercise applying the law and implicit in the life-cycle of every rule,³⁹ is thus necessary to unpack, specify, and clarify the exact meaning of a particular legal norm and determine its content, irrespective of its source.⁴⁰ Not only are CIL rules no exception; they are par excellence a case in point due to their unwritten character, and all the more so it there is no case law or precedent relating to the situation in which the CIL rule is to be applied.⁴¹ This section will first outline the peculiarities of the interpretative practices and methods the CJEU employs (Section 3.1), and then identify and analyse the patterns revealed in relevant case law where the CJEU has engaged with CIL and its interpretation (Section 3.2).

3.1 The CJEU and Interpretation of EU Law: The Basics, in Brief

Unlike traditional international courts, whose authority to interpret international law is on an equal footing with that of national courts and which in principle do not have compulsory jurisdiction nor operate as part of a co-ordinated scheme, the CJEU is entrusted with the authentic interpretation of EU law and there is clear division of labour between it and the member states’ national courts.⁴² Also, the CJEU exercises exclusive and compulsory jurisdiction over matters falling under the EU treaties, having in this respect a role resembling to that of states’ constitutional or supreme courts.

As a result, the CJEU has rapidly affirmed its interpretative practices and methods, which are somewhat different from those in international law. It applies methods that are similar to the interpretive techniques of a domestic constitutional court,⁴³ albeit with variations on a number of points. As early as the Van Gend en Loos case, the CJEU identified three key interpretative methods it employs – namely, giving consideration to ‘the spirit, the general scheme and the wording of [the] provisions [of EU law]’⁴⁴ – which can be readily equated with, respectively, teleological, systemic, and grammatical interpretation of the law (generally applied in that order of priority in CJEU practice).

3.2 The CJEU Interpreting CIL: Exploring and Understanding the Patterns

The intellectual process consisting in interpreting the law must be distinguished from the identification of a CIL rule (i.e. determining the existence of such a norm). In accordance with Merkouris’s fundamental distinction, interpretation is a deductive process after a given CIL rule has come into existence, whereas identifying a CIL rule is more of an inductive exercise.⁴⁵ Once a CIL norm has come into being (i.e. has implicitly been endorsed by the international community through state practice and opinio juris), its subsequent application in particular cases in the course of its lifespan will be subject to the deductive process of interpretation. What is mistakenly called ‘interpretation’ of state practice (or of both constitutive elements of a CIL norm) – an exercise that would be better termed the ‘qualification’, ‘assessment’, or ‘evaluation’ of the formative elements of CIL – should not be conflated with, and thus needs to be distinguished from, interpretation strictly speaking subsequent to the rule’s emergence.⁴⁶ ‘In this manner, interpretation focuses on how the rule is to be understood and applied after the rule has come into existence.’⁴⁷ However, some grey zones and overlaps persist. Let us take the example of exceptions under a given CIL rule. It might be debated whether delimiting the scope of particular exceptions is a purely deductive exercise, as such qualifying as interpretation; or whether recourse to the two-element test (assessment of state practice and opinio juris) is again necessary to determine whether such an exception exists as a self-standing rule, an exercise qualifying as identification of a CIL norm that is incidentally an exception to the main customary rule.⁴⁸ Another grey area is the dynamic relationship between a rule and its exceptions, which ‘may well change and evolve over time or even on a case-by-case basis’.⁴⁹

When the CJEU interprets CIL norms forming an integral part of the EU legal order, its interpretation – given that its rulings are binding erga omnes – also binds the member states, and consequently influences their practice and opinio juris. In other words, CJEU judgments engaging with CIL rules have a ‘multiplying’⁵⁰ or ‘snowball’⁵¹ effect. Below we discuss four examples of CIL norms dealt with by the CJEU that well illustrate its approach to the interpretation of customary international law.

3.2.1 State Immunity from Jurisdiction

Let us first consider the scope and content of the CIL norm affirming the immunity of states from jurisdiction, which protects them from being sued in the courts of another sovereign state.⁵² The ICJ has also engaged with the interpretation of this CIL norm, which demonstrates its importance in the international legal order.⁵³ The two leading CJEU judgments in this field – Mahamdia (C-154/11) and Rina (C-641/18) – are worth analysing together, given that the latter builds on and refers to the former. Both cases concerned the interpretation of the CIL rule of state immunity from jurisdiction as part of the EU legal order. In Mahamdia, the core legal issue was whether, in view of the jurisdictional immunity of states, it was possible for the dismissal of a worker who had been employed as a driver by a non-EU member state (Algeria) at its embassy in a member state (Germany) to be challenged in the courts of that member state. In Rina, the key issue was the application of the CIL rule of state immunity to private bodies to which a sovereign state (here Panama) has delegated the discharge of duties under international law (certification and classification of ships).

The outcome of the two cases was similar, confirming the relative nature of state immunity (as opposed to the classic understanding of it as absolute), but they touched on different aspects of this complex legal relationship. Mahamdia was limited to defining a state’s immunity (that of Algeria) in a labour-related dispute: the CJEU found that employment-related court action concerning a member of an embassy’s non-diplomatic staff brought in the country where the embassy was located did not fall within the scope of immunity from jurisdiction enjoyed by the embassy’s home state before the courts of another country, for the chauffeur’s dismissal by the embassy was an act performed jure gestionis.⁵⁴ The Rina ruling approached the question of immunity from another angle when stating that private actors do not enjoy automatic immunity from jurisdiction simply because states have delegated the performance of international obligations to them⁵⁵ – an interpretation that also avoids the risk of immunity destroying any legal action whatsoever.⁵⁶ In other words, the certification and classification of ships by private law bodies acting on behalf of third states (here Panama) do not qualify as acts performed jure imperii. In both of these cases the CJEU limited the ratione materiae scope of the CIL rule on immunity from jurisdiction by allowing for certain exceptions, such as disputes over contracts of employment and the activities of classification/certification of ships by private entities.

The CJEU’s examination of the material scope of the customary norm of state immunity from jurisdiction was marked by a peculiar division of labour between the Advocates General and the bench of the court. After recognizing a lack of clarity and uncertainties around the customary rule of state immunity, the Advocates General carried out the substantive and in-depth, analysis of the meaning and (possible) material scope of state immunity and its exceptions. The outcome of this legal analysis (i.e. the contextual interpretation of the CIL norm) was in essence taken up by the CJEU in its rulings themselves, which simply refer to the key findings in the opinions of the Advocates General, thereby merely asserting the CIL rule or the meaning the Advocates General accorded to it,⁵⁷ rather than citing or referring to any international legal materials supporting this conclusion.

In both cases, the interpretative engagement consisted in the difficult task of distinguishing between state acts performed jure imperii and those performed jure gestionis. The most intricate question lays in drawing a dividing line between these two types of acts and how to classify certain acts, including when a state acts as an employer and when a state’s action is ‘to some degree privatised’.⁵⁸ The interpretation of the customary principle of state immunity – and the aforementioned division of labour between the Advocates General and the CJEU in this exercise – is well illustrated by Advocate General Mengozzi’s compelling comment in Mahamdia on the contemporary challenges faced in deciding whether certain acts of states are shielded from legal proceedings before foreign courts:

The modern State has become a polymorphous actor in law and may act and enter into legal relations without, however, exercising its sovereignty or its public authority in doing so: I am thinking in particular of the State as a trader, but also, of course, the State as an employer. Because these different facets of the State’s legal activity are not systematically accompanied by the exercise of powers as a public authority, they tend no longer to justify the automatic recognition of immunity from jurisdiction.⁵⁹

The CJEU subsequently endorsed this interpretation in its judgment by summarily recalling the Advocate General’s above observation about the exercise of public powers and its implications.⁶⁰

Against this backdrop, the most intriguing question for present purposes is, what methods did the Advocates General and then the CJEU use to arrive at the conclusions reached? After recalling that state immunity is a corollary of the international law principle par in parem non habet imperium (a state cannot be subjected to the jurisdiction of another state),⁶¹ the interpretative exercise focussed on delimiting the boundaries of possible exceptions to the main rule (state immunity), entailing that acts performed jure gestionis fall outside the exercise of public powers and do not enjoy immunity. In essence, this exercise involved adducing evidence, of both state practice and opinio juris, that would substantiate the existence of such exceptions. In other words, the interpretation of the CIL norm (states enjoy immunity from jurisdiction) consisted not in applying systemic or teleological interpretative methods but rather in proving that certain exceptions exist as special, self-standing ‘mini-rules’ that still formed part of, and were derived from, the larger CIL principle. This approach can qualify as a sort of logical interpretation, carving out an exception and determining its content and limits within the boundaries of the ‘mother’ CIL norm, while also refining and chiselling it (states enjoy immunity from jurisdiction save for their acta gestioni). In this endeavour to delimit the scope of state immunity (or, conversely, that of permissible exceptions to it), the Advocate General opted for the concept of relative immunity and applied the two-elements method to prove its general acceptance as a custom:

a rule of customary international law will only exist where a given practice actually exists that is supported by a firm legal view (opinio juris), that is to say, where a rule is accepted as law. It is in the light of that principle that it is necessary to determine whether, in accordance with the doctrine of relative immunity, the content of the principle of State jurisdictional immunity is such that the defendants may claim immunity.⁶²

With a view to underpinning the concept of ‘relative immunity’ based on the fundamental distinction between acts performed jure imperii and those performed jure gestionis, the Advocate General turned to national legislation, domestic (German) case law, the jurisprudence of the ECtHR,⁶³ some (not widely ratified) conventions (heavily relying on their terms and regulatory logic)⁶⁴ and academic publications for evidence.⁶⁵ This technique of referring to a range of written instruments and case law which codify/recognize the above variant of the customary norm can be regarded as systemic interpretation.⁶⁶ Persuaded that the origins of state immunity lay in the sovereign equality of states, the CJEU took the above-described assessment for granted and relied on this qualification in both judgments, opting for the relative nature of state immunity with the simple assertion that the doctrine of relative immunity replaced that of absolute immunity in our times.⁶⁷ Nonetheless, the CJEU added in Rina, as an extra argument corroborating this position, that a recital in a piece of EU secondary law⁶⁸ ‘bears out the legislature’s intention to give a limited scope to its interpretation of the customary international law principle of immunity from jurisdiction with regard to classification and certification of ships’.⁶⁹ This statement can also be considered as the expression of the emergence of a regional (European) CIL rule⁷⁰ on the matter – given that the EU exercises some of the public powers of its member states and the practice (here, law-making) of the organization may be equated with the practice of the member states.⁷¹ In other words, the EU has functionally replaced the member states in a number of areas, including the one governed by the EU directive containing the recital quoted above, and were EU practice not taken into consideration in its own right as contributing to (regional) CIL norms, then ‘Member States themselves would be deprived of or reduced in their ability to contribute to State practice.’⁷²

3.2.2 Right of Self-Determination and States’ Permanent Sovereignty over Their Natural Resources

The series of cases concerning the legality of extending the application of EU–Morocco trade and fisheries agreements to the territory of Western Sahara – Front Polisario I,⁷³ Western Sahara Campaign UK,⁷⁴ and Front Polisario II⁷⁵ – serves as another springboard for scrutinising the CJEU’s engagement with the interpretation of CIL norms, notably the right of self-determination (of the people of Western Sahara in these particular cases) and states’ permanent sovereignty over their natural resources as a corollary thereto.

Chronologically, it was in Front Polisario I that an Advocate General first engaged in an interpretation of the CIL principle⁷⁶ of states’ permanent sovereignty over their natural resources and, to some extent, a people’s right of self-determination. In his succinct analysis, the Advocate General did not make it clear whether the former is derived from the latter (which is the position generally accepted among international lawyers⁷⁷); despite his silence on this matter, he nonetheless discussed permanent sovereignty over natural resources, which he considered as being somewhat anchored to the right of self-determination. When interpreting the meaning of the CIL principle of permanent sovereignty over natural resources and exposing its content and implications, the Advocate General relied⁷⁸ on the language and formulations of a series of UN General Assembly resolutions,⁷⁹ following the – criticised⁸⁰– method applied by the ICJ in the Democratic Republic of the Congo v Uganda case.⁸¹ Remarkably, however, and without explanation, he saw no erga omnes obligations implied in this CIL norm – unlike the two dissenting ICJ judges in the East Timor case,⁸² the African Union⁸³ and several commentators,⁸⁴ all of whom have embraced the view that permanent sovereignty over natural resources is an essential principle of contemporary international law with erga omnes effect. As a consequence of this particular line of reasoning, the Advocate General concluded that permanent sovereignty over natural resources ‘cannot establish the liability of the [EU] as the obligation not to recognise as legal a situation resulting from a serious infringement of an erga omnes obligation and not to render aid or assistance in maintaining that situation does not apply’⁸⁵ and, more broadly, the EU and its institutions cannot even infringe this obligation since they are not bound by it. Without going into a detailed critique of this statement, suffice it to say that this reasoning is hardly reconcilable with the CIL nature of this principle, which as such is an integral part of the EU legal order.

There is in turn no mention of permanent sovereignty over natural resources in the CJEU’s judgment, which instead focussed on the right of self-determination, without contemplating the possibility that its force field might extend to the CIL principle of permanent sovereignty over natural resources. Actually, the CJEU refrained from genuinely interpreting the right of self-determination. It essentially restated the basics concerning this right’s addressees and beneficiaries (non-self-governing territories and peoples who have not yet achieved independence) and legal nature (a legally enforceable erga omnes right),⁸⁶ relying on the authority of an advisory opinion and a judgment handed down by the ICJ,⁸⁷ along with the 1970 UN General Assembly Resolution on Principles of International Law Concerning Friendly Relations and Co-operation among States.⁸⁸ The rest of its engagement with the principle is limited to the application of the norm in the specific context of Western Sahara as a non-self-governing territory, and is irrelevant to the subject under discussion here.

In Western Sahara Campaign UK – which was the second episode in this saga – the Advocate General started his analysis with the right of self-determination, which, following the textbook approach,⁸⁹ he characterised as a human right. This legal qualification better served the purposes of the EU legal order, as the concept of self-determination was thus squeezed into the category of fundamental rights as ‘general principles of EU law’.⁹⁰ Through this move, the Advocate General could comfortably resort to the classic, judge-made interpretation techniques employed in unpacking the meaning and content of certain fundamental rights as general principles of EU law – namely, drawing inspiration from the guidelines supplied by international instruments for the protection of human rights ‘on which the Member States have collaborated or to which they are signatories’.⁹¹ For this exercise, he relied on the International Covenant on Civil and Political Rights, the International Covenant on Economic, Social and Cultural Rights, the 1975 Helsinki Final Act, and ‘several international authorities and instruments and … academic literature’, as well as the jurisprudence of the ICJ.⁹²

The Advocate General then went on to examine the right of self-determination as a (customary) principle of general international law with erga omnes effect. What is most interesting here is the way the Advocate General analysed whether this customary rule reflected a ‘clear and precise obligation which is not subject, in its implementation or effects, to the adoption of any subsequent measure’.⁹³ Under EU law, these represent the criteria according to which a customary norm will have direct effect and hence can serve as a benchmark of legality for secondary EU legislation. To underpin this characterisation, the Advocate General first relied on the CJEU’s ruling in Front Polisario I and the ICJ’s advisory opinion in Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory,⁹⁴ followed by a number of international instruments affirming the right of self-determination where ‘the content of that right is stated in detail’.⁹⁵ As a result of this interpretative analysis, he concluded that, from the viewpoint of its content, the customary law principle of self-determination is unconditional and sufficiently precise. It is thus sufficiently sharp-toothed to operate as a standard of conformity for assessing the validity of an allegedly contradictory piece of secondary EU law. Put differently, the outcome of this interpretative exercise boosted this principle’s normativity and raised its judicial enforceability to a higher level.

Turning to the CIL principle of states’ permanent sovereignty over their natural resources, the Advocate General rectified his position taken in Front Polisario I and held that this customary principle is binding on the EU – which can be seen as an implicit recognition of its erga omnes effect, contrary to Front Polisario I. In the subsequent analysis, the Advocate General found interpretative guidance in a new ‘source of (soft) law’ – a letter of 29 January 2002 from the UN Under-Secretary-General for Legal Affairs to the president of the UN Security Council, seeking to demonstrate that ‘the exact legal scope and implications [of the principle of permanent sovereignty over natural resources] are still debatable’,⁹⁶ including how to determine what constitutes exploitation of natural resources for the benefit of the people of a non-self-governing territory. The Advocate General went on to conclude that despite the uncertainties concerning the exact contours of this obligation inherent in this customary concept,⁹⁷ the principle of permanent sovereignty over natural resources is equally a sufficiently clear and precise norm, capable of forming the basis for a judicial review of acts of EU institutions,⁹⁸ including decisions concluding international agreements on behalf of the EU. These interpretative developments since the Front Polisario I case are noteworthy – although, here again, the Advocate General failed to discuss the ties between the right of self-determination and the principle of permanent sovereignty over natural resources, shedding no light on whether he considered the latter as logically flowing from the former.

Strange as it might seem, the CJEU did not engage with the right of self-determination or its corollary principle of states’ permanent sovereignty over their natural resources in this case either. There is just a passing mention of self-determination as a rule of general international law, without any interpretive engagement with this CIL norm⁹⁹ − a mere assertion its customary nature based on ICJ case law and select UN General Assembly resolutions. The CJEU’s tight-lipped approach to these two applicable CIL rules, which by contrast are discussed at length by the Advocate General, is even more restrained than in Front Polisario I. Its highly reserved stance might be explained by the fact that the EU Court had already set out the basic characteristics of the right of self-determination in its earlier ruling relating to the non-self-governing territory of Western Sahara and did not feel compelled to repeat those, and could simply refer to its findings in Front Polisario I by employing cross-references to this judgment tout court.

Most recently, the General Court reiterated the CJEU’s statements on the customary character of the right of self-determination in Front Polisario II, referring to the same international legal authorities, including the ICJ and select UN General Assembly resolutions, as had been earlier relied upon by the Court of Justice.¹⁰⁰ However, no further interpretation followed: the General Court simply concluded that the people of Western Sahara enjoyed the right of self-determination¹⁰¹ and then went on to focus on the more specific, technical (EU law) questions of the case without needing to delve further into the CIL character of the norm at hand.

The three cases outlined above show that neither the Advocate General nor the Court of Justice or the General Court have gone much beyond the mere identification of applicable rules of customary international law. There was very little interpretative engagement with the customary norms at issue; the discussion was instead rather technical, referring to international instruments of a general character (as CIL has been codified in quasi-universal conventions or enshrined in UN General Assembly resolutions) or to selected passages from leading ICJ judgments (or those of its predecessor). Consequently, the EU Court did not really engage in the exercise of complex interpretation of a CIL norm, but simply relied on other authoritative international legal materials, which it accepted as sufficiently illuminating on the meaning and (some aspects of) the content of a given CIL norm such as the right of self-determination and its derivative principle of permanent sovereignty over natural resources. With respect to the legal nature and possible legal effects of both CIL norms, greater novelty can be found in the opinions of the Advocates General, who recognised that, given their unconditional and sufficiently precise character, the norms could be invoked by private parties in court proceedings (direct effect).

It is noteworthy that the way the CJEU’s apprehends the relationship between the right of self-determination and the permanent sovereignty over natural resources is somewhat similar to the ICJ’s approach in deriving a norm from another CIL rule. The CJEU did not take a clear position on the relation between the latter CIL norm and the former, asserting its customary nature by simply invoking some supporting international legal materials. There have been cases in which, similarly, the ICJ ‘merely derived one legal standard from another without the exposition of specific state practice and opinio juris’.¹⁰² Examples include Questions Relating to the Seizure of Certain Documents, where a state’s right to communicate with its counsel and lawyers in a confidential matter was considered to stem from the principle of sovereign equality of states;¹⁰³ and the Corfu Channel case, where the specific obligation to give notification of the existence of a minefield in the Albanian territorial waters was held to derive from certain general and well-recognised principles, including every state’s obligation not to knowingly allow its territory to be used for acts contrary to the rights of other states.¹⁰⁴ In these cases, the ICJ did not make it clear whether the derived, more specific obligations of a CIL nature were self-standing rules in their own right; hence, it did not carry out a full-fledged two-element assessment to determine the existence of these particular customary rules and ‘thus freed itself from having to look for new evidence supporting’ them.¹⁰⁵ This approach can be defended, though: it would not only be asking too much in every single case where an otherwise general customary concept is applied to individual circumstances, but also shows the power of interpretation of CIL. This argumentative technique finds support in the work of the ILC: the commentaries to the Draft Conclusions on the Identification of Customary International Law likewise acknowledge that:

The two-element approach does not in fact preclude a measure of deduction as an aid, to be employed with caution, in the application of the two-element approach, in particular when considering possible rules of customary international law that operate against the backdrop of rules framed in more general terms that themselves derive from and reflect a general practice accepted as law.¹⁰⁶

Against this backdrop, there is every reason to agree with the illuminating remarks of Chasapis Tassinis in this regard:

By largely ignoring the concept of interpretation, our operating theories of custom may seem to reduce the complexity of that source by putting virtually all of the emphasis on gathering the appropriate evidence. … Factoring interpretation into our analysis of customary international law may thus make identification seem less arbitrary while opening up more productive avenues in legal reasoning about this fundamental source of international law.¹⁰⁷

3.2.3 Obligation Not to Defeat the Object and Purpose of a Signed Treaty prior to Its Entry into Force

A further situation in which the CJEU engages with the interpretation of CIL is when it acknowledges that a certain principle of EU law that it is developing has its origins in customary (general) international law or states that an existing general principle of EU law is actually a corollary of a very similar CIL norm. The outcome of this interpretative exercise is basically the ‘mirroring’ or ‘re-packaging’ of the original CIL norm, for the purposes of the EU legal order, into a general principle of EU law, with all the legal implications that follow (e.g. the addressees of the norm are no longer merely states but also individuals and private operators; different legal effects kick in, including supremacy and direct effect, etc.). The case of Opel Austria, which concerns the interpretation of the CIL obligation not to defeat the object and purpose of a signed treaty pending its entry into force, is a famous example of that ‘re-packaging’ or ‘mirroring’ technique.¹⁰⁸

It is well known that many rules codified in the 1969 and 1986 VCLT reflect CIL. One key customary provision is the obligation laid down in their common Article 18, according to which:

[a state/international organisation] is obliged to refrain from acts which would defeat the object and purpose of a treaty when:

1. (a) it has signed the treaty or has exchanged instruments constituting the treaty subject to ratification, acceptance or approval, until it shall have made its intention clear not to become a party to the treaty; or

2. (b) it has expressed its consent to be bound by the treaty, pending the entry into force of the treaty and provided that such entry into force is not unduly delayed.

The General Court referred to and applied this principle of a customary nature – which, in essence, is a concrete manifestation of the general principle of good faith – in Open Austria,¹⁰⁹ although its reasoning and the operative part of the ruling was in the end not based on this international legal rule setting out a so-called interim obligation. The case concerned the validity of an EU regulation subjecting gearboxes produced by General Motors Austria to 5,9 per cent customs duty. Opel Austria challenged this additional customs levy imposed in response to alleged Austrian state aid, arguing that the contested regulation was in breach of the customary principle of good faith as codified in Article 18 of the 1969 VCLT. The contested regulation was adopted by the Council of the EU in December 1993, after the instruments of ratification of the Agreement on the European Economic Area (EEA) were exchanged¹¹⁰ but before the EEA Agreement entered into force in January 1994. The EEA Agreement prohibited the imposition of any further customs duties between contracting parties. The General Court accepted the applicant’s arguments that the then European Community was bound by this customary interim obligation as codified in Article 18 of the VCLT, which, it found, was the corollary of the EU law principle of the protection of legitimate expectations. Yet, as it was not convinced that private parties could rely directly on this customary principle of international law, it finally based its ruling quashing the contested regulation on the protection of legitimate expectations as a general principle of EU law,¹¹¹ which could be invoked by individuals and private operators. Subsequent cases have seen the CJEU clinging to the application of the principles of legitimate expectation and good faith as general principles of EU law, rather than relying on the customary interim obligation enshrined in Article 18 of the VCLT, even if the parties to the dispute based their arguments, at least in part, on this CIL principle.¹¹² This approach reveals the difficulties and uncertainties that not only contracting parties but also private entities risk encountering when, in a legal dispute, they directly invoke the CIL obligation not to defeat the object and purpose of a treaty.¹¹³

The above reasoning allowed the CJEU to assert the autonomy of EU law, portraying it as an independent legal system that does not derive its authority from international law – and, in its own legal order, to apply general principles of EU law instead.

3.2.4 Territorial Scope of Treaties

The last example is also taken from the realm of the law of treaties. It is noteworthy that the CJEU almost always interprets customary law when resorting to VCLT rules, given that the EU is not bound by the VCLT itself but only by the equivalent customary rules and principles of treaty law that exist in parallel to the written instrument. Leaving aside the practice of the EU judiciary concerning the interpretation of the customary rules of treaty interpretation (as reduced to writing in Article 31 VCLT), an illustrative example from the realm of the law of treaties is where the CJEU (re-)interpreted the CIL rule on the territorial scope of treaties. The customary rule governing the territorial scope of treaties is codified in Article 29 VCLT, in a quite laconic manner, as follows: ‘Unless a different intention appears from the treaty or is otherwise established, a treaty is binding upon each party in respect of its entire territory.’

At first sight, this provision looks straightforward and does not seem to call for further clarification. Yet, the complexities of the Front Polisario I and Western Sahara Campaign UK cases led the CJEU to engage with this rule and to attempt to deconstruct its components. In this process, the CJEU found support in international treaty-making practice¹¹⁴ and pointed out that those treaties which apply beyond the territory of a state use the expressions ‘under [the] jurisdiction of that State’¹¹⁵ or ‘any of the territories for whose international relations it is responsible’.¹¹⁶ Given that ‘territory of a state’ is nowhere defined in international law, but rather thought to be self-explanatory, the CJEU then offered its own construction of ‘territorial scope’ as follows:

a treaty is generally binding on a State in the ordinary meaning to be given to the term ‘territory’, combined with the possessive adjective ‘its’ preceding it, in respect of the geographical space over which that State exercises the fullness of the powers granted to sovereign entities by international law, to the exclusion of any other territory, such as a territory likely to be under the sole jurisdiction or the sole international responsibility of that State.¹¹⁷

As result of this interpretation, and coupled with the principles of good faith in performing treaties and the relative effect of treaties, the CJEU drew the conclusion that, as a non-self-governing territory, the Western Sahara was by no means under the territorial scope of the EU–Morocco bilateral fisheries agreement.

Some commentators,¹¹⁸ citing the travaux préparatoires of the VCLT,¹¹⁹ note that the customary rule enshrined in Article 29 VCLT was basically intended to set out a general rule concerning the territories of the state parties which applies as a fall-back clause in situations where a treaty does not define its territorial application. As Odermatt points out, ‘[t]he CJEU, however, gives much more significance to this provision, interpreting it to mean that a treaty only applies with respect to territory over which a state exercises full sovereign powers, unless there is an express provision providing for its application to other territory’. Does this mean then that the CJEU has re-interpreted a CIL norm, setting out stricter requirements for (EU member) states and the EU itself to follow when determining the territorial scope of their treaties? Kassoti answers affirmatively by insisting that as a result of this interpretation, whenever a treaty concluded by the EU is intended to produce extraterritorial effect its ‘territorial scope’ clause must be worded in such a way as to expressly provide for this effect.¹²⁰

4 Lessons Learnt and Take-Aways

Any court that applies and interprets CIL rules does so in a specific legal and institutional context, and this goes for the CJEU, too. The way in which the CJEU interprets customary international law is largely influenced by the role customary international law plays in the cases brought before it. As pointed out in Section 2, a CIL rule is traditionally applied before the CJEU for the purpose of interpreting and elucidating the meaning of provisions of secondary EU legislation.¹²¹ Interpretation to ensure the consistency of EU law with CIL is a limited form of interpretive engagement by the CJEU with a particular CIL norm, for normally it is not the CIL rule that is at the centre of attention in the interpretative process but an EU law provision. As a result, the main task for the CJEU is not to interpret the CIL rule (which occupies a subsidiary position in this scenario) but, once it has found a relevant international legal rule and identified it as being of a customary nature, to use that rule as broader legal context, also binding on the Union, for the interpretation of the EU law provision at hand. A typical example of such use of a customary rule is when the CJEU is confronted with questions treaty law when dealing with an EU agreement and employs the VCLT ‘rulebook’ largely reflective of CIL. In other words, this is a sort of an interpretation of customary rules by proxy: the CJEU essentially interprets a VCLT provision not as a treaty rule – as the EU is not bound by the VCLT, it cannot legally engage with it as such – but as its customary law equivalent. The ruling in Opel Austria went even further by re-packaging the customary rule of not defeating the object and purpose of a signed treaty prior its ratification and, for the purposes of Union law, mirroring, as it were, its content in a general principle of EU law – namely, the protection of legitimate expectations. Likewise, when interpreting the CIL rule relating to the territorial scope of a treaty, the EU Court opted for a significant (restrictive) change to its meaning, reformulating the customary rule as crystallised in Article 29 of the VCLT and redefined it with more stringent requirements.

A specific form of employing CIL as an interpretive tool to clarify the meaning of EU law came up in the Mahamdia and Rina cases, where identifying the relevant CIL norm (the jurisdictional immunity of states) was not the most crucial task. The peculiar character of this CIL principle in procedural terms – i.e. denying the injured private party access to justice, which touches on a foundational value in the EU legal order: the right to an effective judicial remedy – required that the meaning, the boundaries, and the exceptions of state immunity be thoroughly examined before the CJEU could answer the questions concerning the interpretation of certain provisions of the Brussels II Regulation on exercising jurisdiction in civil and commercial matters. Despite the key role of this CIL rule, it was the Advocate General alone who engaged in a proper interpretation of the norm, opting for its systemic and evolutive interpretation, the outcome of which was taken up by the CJEU as a pre-cooked finding.

In theory, the interpretation of a CIL norm could play a more central role before the CJEU when (private) parties rely on it as the review standard for challenging the validity of a legal act adopted by the EU institutions. This scenario, which occurred for the first time in the ATAA case, forces the CJEU to interpret the invoked CIL rule, and notably to run the two-pronged test developed in CJEU case law to determine the direct effect of the CIL rule – that is, whether the customary norm at hand is capable of calling into question the competence of the EU to adopt a given piece of secondary legislation and whether it may affect the rights that individuals derive from EU law.¹²² The CJEU was faced with this question in the series of cases where Front Polisario relied on the customary right of self-determination and the permanent sovereignty over natural resources as grounds for invalidating the contested bilateral agreements between the EU and Morocco. Again, despite lengthy and illuminating legal analyses of the meaning and content of these CIL rules by the Advocates General, the CJEU opted for a different (and somewhat evasive) line of reasoning, resorting to the rules of treaty interpretation so as to avoid having to assess the legality of the contested EU acts against these customary norms of key significance.

What can one distil from the above observations? The selected rulings we have discussed demonstrate that the CJEU has been reluctant to undertake its own investigation into state practice and opinio juris in order to interpret a given norm of customary international law, most often stopping long before by simply asserting the existence of the CIL norm without conducting a deeper analysis. (It must be admitted that avoidance of the two-element test is not unusual in the case law of international and domestic courts.¹²³) Instead, the CJEU preferred to refer to the case law of other international courts and tribunals, particularly the ICJ,¹²⁴ and occasionally select instruments of international law enshrining the customary rule in question (such external referencing can been regarded as a co-ordination technique to ensure consistency¹²⁵). Other avoidance techniques on the part of the EU Court can also be observed. They include merely copying and pasting, in condensed form, the main findings of the interpretive analysis carried out by the Advocate General (Mahamdia and Rina); replacing the CIL norm in question with a corresponding general principle of EU law (Opel Austria); or simply looking for ‘safer’ avenues of legal reasoning, notably ‘interpreting away’ vital issues of CIL by using the toolbox of treaty interpretation and not touching on questions of interpretation of substantive customary rules of fundamental importance (such as the right of self-determination and the permanent sovereignty over natural resources) (Front Polisario I-II and Western Sahara Campaign UK).

Analysing the CJEU’s judicial practice is an opportunity to explore the possible reasons and motivations behind the CJEU’s guarded approach to the interpretation of CIL rules once they have been included in the set of legal norms applicable to a particular case. These reasons are manifold. First, the CJEU perceives its role as being more that of a domestic court than an international court, as a result of which it displays restraint when engaging with the interpretation of CIL that lies outside its comfort zone. Similar discomfort and hesitation can be seen in domestic courts,¹²⁶ where CIL norms raise difficulties in terms of ascertainment and legitimacy. Second, the EU Court’s unease may be linked to a lack of resources and specialised knowledge in public international law,¹²⁷ which is compounded by the fact that in certain cases the CJEU has to prove the existence of state practice and opinio juris not only at the EU level but also in the international arena,¹²⁸ which is usually unchartered territory for the CJEU. A third explanatory factor is that, unlike the treaties to which the EU is a party, the EU has not given its explicit consent to CIL norms and may have had no role in their development. Customary international law is thus seen as something developed ‘outside’ the EU legal order and should therefore be ‘mistrusted’.¹²⁹

To sum up, the CJEU’s engagement with the interpretation of CIL and its interpretation techniques – unlike the approach of the Advocates General in a number of instances – remain underdeveloped. There is thus room for improvement, including with a view to enhancing the CJEU’s output legitimacy. This author agrees with those scholars who argue that the CJEU’s application of CIL will be fully legitimate procedurally only if the accompanying interpretative reasoning is significantly improved.¹³⁰ Boldly asserting certain CIL rules without additional refinement and substantiation fails to convince other interpreters of international law. As most perceptively observed by Higgins, the CJEU’s caution when it comes to CIL stands ‘in marked contrast to the confidence shown as to its capabilities in international law shown by the Court in other cases’.¹³¹ With the expansion of the EU’s treaty-making activities¹³² and its rising profile as a major (legal) actor on the global stage,¹³³ the number of cases before the CJEU pertaining to international law will continue to grow, which will make it all the more desirable for the EU Court to deal with these issues, including the interpretation of CIL, with greater confidence and authority.

This is the case in particular when several CIL rules are to be applied simultaneously and their relationship needs to be determined. A similar need arises, in a more dramatic fashion, where conflicting CIL norms apply in one and the same case before the CJEU. The time is ripe for a deeper and more convincing engagement with CIL on the part of the CJEU through reliance on a conceptually and methodologically sound framework for interpretation that will strengthen the unique judicial function it performs.

8 Judicial Effectiveness or Judicial Ambiguity Is CIL Identification an Instrument for Judicial Activism in Excess?

Leoni Ayoub

1 Introduction

Effectiveness and efficiency in judicial decision-making are the most important objectives of any court. While this concerns primarily the final decisions that are rendered, this is also relevant to the judicial process and the legal reasoning that a court or tribunal carries out to reach its decision, in order to ensure continuity and coherence. Traditional understandings of the international judiciary have seen the judges’ role as one where they discover and declare the law by applying it at face value to the legal issues that have arisen within the case, thereby achieving effectiveness through what is said to be direct and clear application of the law.¹ Indeed, ‘[international] judges have to apply the law and they have to apply the law in force’.² This would seemingly contrast with the picture of the judge as one who engages in developing the law in order to administer justice. This latter understanding sees the judges’ role as involving an inherent form of creativity to meet the needs of the case before them,³ while they may be accused of entering the field of law creation.

This dichotomy sits rather uneasily with the identification of customary international law (CIL), which is by its very nature unwritten and established by identifying evidence of state practice and opinio juris.⁴ Accordingly, custom needs to be understood as ‘the result of an informal process of rule-creation’.⁵ This two-pronged approach to recognising CIL renders the degree of precision that is usually found in conventional law-making processes more difficult to achieve.⁶ This is because of a paradoxical difficulty that exists between qualifying the rule as law while simultaneously seeking to apply and interpret it. This may lead to instances where courts are considered to assume the position of legislator by overstepping the powers granted to them, laying them more easily open to the reproach of engaging in judicial activism.

Although the concept of judicial activism has come to be frequently associated with the decisions of certain international courts,⁷ it has particularly derogatory connotations, evoking the seemingly unorthodox judge who has taken the decision to derogate from established law and base their decision on a novel, or at least less common, interpretation of a legal principle. This raises the question of the possible role of activism in the determination of certain customary rules and the part it plays in their subsequent effectiveness or ambiguity.

The aim of this chapter is to examine instances of judicial activism in the decision-making of international courts and tribunals during the determination and application of CIL and how that allows for either judicial effectiveness or ambiguity. To do this, we will first set out the foundational parameters that need to be examined. We will describe the process by which custom is created and set out the customary rule on which our analysis will focus – namely, the indispensable parties principle.⁸ We will then turn to judicial effectiveness, its definition and consequence for the judicial function, and in particular how it can be identified. We will then provide a definition of, and guidelines for identifying, judicial activism in international courts. With these elements in mind, the discussion will then return to an analysis of relevant case law regarding the indispensable parties principle and the use, or not, of judicial activism in such cases. Lastly, we will evaluate whether custom has been used as an instrument for judicial activism and, if yes, enquire into how the judicial function itself has enabled this.

2 CIL and the Judicial Process

Typically unwritten, CIL is determined through state practice and acceptance as law (opinio juris). Nevertheless, the recognition of customary international rules remains a difficult task,⁹ as it requires a particular process through which the interpreter (the judge) can arrive at a conclusion of the existence of a law or rule under custom. ¹⁰ Further, the question arises as to what extent the courts engage in the identification and determination of CIL proper or fall victim to what has been termed ‘pulling a rabbit out of [their] hat’ by simply asserting what they think the law is.¹¹

The determination of custom has a direct relationship with the judicial function and the judicial process. As Maarten Bos has argued, proof of custom is a ‘process of thought’ leading to a judicial pronouncement, which thereafter forms undeniable proof of a legal relationship and indicates the existence of a legal norm or law.¹² Thus, the very identification of the customary rule can indicate the judge’s state of mind and, by extension, the possible use of activism or restraint. Furthermore, this process of reasoning to identify a customary rule reflects the progress and evolution of the judicial process.¹³ This is because the element of identifying custom is so intrinsically linked to the judicial process – it being a process itself – that it may shed light as to the judicial function assumed.¹⁴

In a similar vein, the present author considers that the interpretation of custom also reflects the state of the judge’s mind and the ‘process of thought’ followed to arrive at its possible application.¹⁵ Indeed, while methodology in interpretation rests beyond the confines of this analysis, interpretation is more than just deciphering what the language of a rule means; it goes further and asks: ‘What law does this [rule] make? How does it fit into the rest of the corpus juris?’¹⁶ By extension, if interpretation of custom comes in the form of interpretation of previous evidence of state practice and opinio juris, we can identify the ever-evolving judicial function and its role in the creation of the law.

As we will see in the following analysis, the method of identification and interpretation of custom grows to become a vital element in the very creation of the judicial function. By contrast, if this method is lacking, the court has fallen into the trap of ‘pulling a rabbit out of its hat’, contributing to inconsistency and incoherence, where the court simply ‘asserts the law as it sees fit’.¹⁷

2.1 The Indispensable Parties Principle and CIL

As custom forms a broad corpus of law, the present analysis will be confined to the principle of indispensable parties, as articulated by the International Court of Justice (ICJ) in the Monetary Gold Removed from Rome case.¹⁸ Aware of the difficulties surrounding the history and legal origins of this principle¹⁹ and the objections that exist as to its nature as a rule or principle of customary international law²⁰ the present author nevertheless argues that it is precisely this confusion that makes it worth examining, as the role played by the international judiciary in its evolution offers ample scope for discussion. This, in turn, provides the opportunity to scrutinise the work and analysis carried out and to open a discussion on the role of activism and restraint in relation to custom in general.²¹

Recognised in international law as a governing principle and a piece of conventional wisdom,²² this principle essentially affirms that a court or tribunal will not decide a case if the decision will affect the legal rights of a third state which is indispensable to the resolution of the dispute before it. This principle is most often framed as an absolute,²³ yet without any particular source attributed to it.²⁴ Considering that different principles may be derived from ‘different sources of international law at different times and even the same principle may be simultaneously shaped by various elements of the legal order’,²⁵ we can see how the principle can be the result of a variety of sources, one of which could arguably be CIL.²⁶

As this analysis sets out to demonstrate, the indispensable parties principle has by now not only acquired general acceptance within the international legal system but is also called upon quite frequently in practice.²⁷ The principle affords an opportunity to analyse both its identification and its subsequent application as a customary rule: while Monetary Gold may or may not reflect a rule of custom that existed at the time of the ruling, subsequent international courts have allowed us to understand it as such today. Furthermore, as the principle has a procedural character,²⁸ this enables a direct link between judicial effectiveness and judicial activism, because the very need for effective procedures is directly linked to the effective administration of justice.²⁹

3 The Judicial Function and Its effectiveness

Judicial effectiveness in international law is a controversial concept.³⁰ This is but a natural corollary to the diverging opinions of what the judicial function precisely entails and what the role of a judge is. Indeed, various definitions and models of effectiveness have been introduced in an attempt to define the concept of judicial effectiveness.³¹ One common definition is what has been described as the goal-based rationale³² according to which ‘an action is effective if it accomplishes its specific objective aim’.³³ In other words, the court or tribunal must be fulfilling the judicial function which it was tasked to fulfil.³⁴ To do this, one must identify what that judicial function consists of and the desired outcomes it ought to generate:³⁵ international courts and tribunals are created to settle the disputes referred to them, ‘to do justice’ between the litigant states and render a binding judgment.³⁶ By contrast, judicial ambiguity reflects the judge who does not render effective decisions, one who is not able to fulfil the full spectrum of the judicial function, so that the judgment, while possibly resolving the case, also raises ancillary questions as to its effectiveness and coherence. This, of course, can only be measured by defining what that judicial function is. To be able to so define, or measure, the judicial function, three components are proposed that will allow the examination of the decision-making of the courts and tribunals at the international level.³⁷

The first component is the idea that decisions serve a public, in addition to a private, function.³⁸ On the one hand, there exists the commonly accepted task consisting in resolving the dispute between the two parties to the case the so-called private function.³⁹ On the other hand, there exists the public function of an international court, which goes beyond the settlement of that dispute and extends into the realm of positively creating norms that can generate obedience among the members of the community regulated by that system of norms.⁴⁰ This latter function is linked to the proper administration of international justice by helping to create a body of coherent rules and laws and ensuring overall efficiency in judicial decision-making.⁴¹

This is closely related to our second component: the emergence of a ‘new posture of international courts and tribunals [that] is the “spirit of systemic harmonisation”’.⁴² Although the international legal system has been described as fragmented, giving the impression of isolated regimes, there is a growing rapprochement⁴³ and the creation of common standards, as exemplified through court decisions that allow for a more unified system than that which initially meets the eye.⁴⁴ This describes the web that is gradually being woven in the international legal system through progressive collectivisation, with many components of international law being endorsed through mutual recognition and respect between states.⁴⁵ Customary international law forms part of this collectivised web.

Thirdly, while the notion of judicial law-making may be difficult to reconcile with the traditional understanding of the role of the international judiciary, it has come to be accepted that a judge’s role also comprises an element of law creation through its identification, interpretation and application.⁴⁶ This is not to contradict the idea that judges must identify and apply the law at hand, but to argue that, in identifying and applying that law, they are, through the very nature of the judicial process, also creating it. In other words, through the act of judicial reasoning and interpretation, judicial law-making ipso facto exists, in some shape or other, under the guise of judicial interpretation.⁴⁷

For present purposes, effectiveness reflects a combination of these three components. It should be noted that while precedent and any attention given to previous court decisions is largely denied at the international level,⁴⁸ the international judicial function nevertheless aims to create coherence and consistency through its decision-making. The ICJ ascribes considerable authority to previous decisions, over and above the habitual practice of citation.⁴⁹ In fact, it has been said that it ‘commonly formulates new rules under the cover of interpretation’⁵⁰ and, further, that the ‘Court’s interpretation … contributes to the creation of what it finds’.⁵¹

Ambiguity, here, refers not only to judgments that are ineffective or textually unclear, but reflect a judge who deviates from this triad, rendering decisions that neither contribute to norm creation nor form a part of the collectivised web of international law but instead leave the resolution of the dispute unclear and do not necessarily fit within the overall systemised collective. Where the coherence and consistency of a decision are in question, we find ambiguity.

4 Judicial Activism and Judicial Restraint

4.1 A Definition

Before commencing the analysis, it is important that the terms ‘judicial activism’ and ‘judicial restraint’ be defined. As former CJEU judge Pescatore noted ‘[w]hat is described by one as activism is seen by another as a just and necessary safeguard’.⁵² Therefore, the determination of a judicially activist or restraint decision will always be a matter of degree.⁵³ Despite its relatively widespread usage, the term ‘judicial activism’ has no unified meaning. Although judicial activism is commonly attributed to the law-creating nature of the role of judges, and restraint to rejection of that law-creating role, these attributions provide little as to the nature or content of these principles. Indeed, it has even been asserted that ‘judicial activism is simply the label used for decisions one does not like’.⁵⁴

International legal scholars have nevertheless attempted various definitions of judicial activism, which offer some indication as to how it might be discerned. Hugh Thirlway identified two types of activism: activism in the ‘formal sense’, which arises when the judge ‘deals with an issue the decision on which is not essential to the resolution of the dispute before him … [but wishes] to “enrich and develop” the law’;⁵⁵ and ‘substantive activism’, which arises when the judge is ‘dissatisfied with existing law … [and] … will be ready to indulge in something close to open law-creation in order to base his decision’.⁵⁶ Former ICJ judge Kooijmans objected to both activism and restraint before the ICJ, steering away from the ‘destructive trap’ of activism and the ineffectiveness of restraint, ‘which closes windows’,⁵⁷ and introducing instead the concept of ‘proactive judicial policy’.⁵⁸ To him, the judicial role is ‘to utilise those aspects of the case which have a wider interest or connotation in order to enrich and develop the law’.⁵⁹ Lara Pair considered the ‘ultimate criterion for judicial activism’⁶⁰ to be the focus on ‘avoidance of an unjust result’ and ‘creative reasoning rather than strict application of the law’.⁶¹

Judicial restraint has been even more illusory, yet some helpful definitions can also be found. Lauterpacht described a court that exercises restraint as one which ‘refrains from explaining rules in detail’⁶² as it ‘may create … the impression the court was laying down new rules of law’.⁶³ Judge Kooijmans similarly qualified restraint as the court that ‘wilfully abstain[s] from using the opportunity … to provide clarification on a matter which […] is highly controversial’.⁶⁴

Former ECtHR judge Mahoney defined the two concepts in parallel. He did not approach activism and restraint as two ‘conflicting theories as to how judges should go about decision-making’.⁶⁵ Instead, he referred to ‘making interpretation choices’, with judicial activism being ‘neutralised’ by the exercise of judicial self-restraint.⁶⁶ Therefore, activism involves ‘[modifying] the law from what it previously was or was stated to be in the existing legal sources’,⁶⁷ while restraint is a technique necessary in order to move ‘proceedings forward by incremental steps in specific contexts rather than by dramatic leaps in the dark’.⁶⁸ These two forces ultimately work together within judicial decision-making in a ‘coherent path of continuity’.⁶⁹ Activism and restraint are ‘two sides of the same coin’,⁷⁰ both aimed at giving the law a coherent structure.

Judge Mahoney’s description seems to be the one best suited to the nature of the international judicial function and the legal system within which it acts. Viewing the two notions in terms of their complementarity is an effective way of understanding activism and restraint, transcending traditional black-and-white definitions to better reflect the true nature of the judicial process. After all, ‘rules are not picked from trees’:⁷¹ even if the legal principles are clear and the law is clearly enunciated, ‘someone’ will have had to develop them – a competent law-determining agency, a court.⁷²

4.2 Identifying Activism and Restraint within the Overall Context of International Law

With the above in mind, identifying activism and restraint remains a difficult exercise, as observed through the lack of any such theoretical framework within the literature on international law.⁷³ Further, identifying activism and restraint must be placed within the overall context of the international legal system, whose characteristics are inseparably linked to how and why certain decisions may or may not be considered instances of judicial activism.

One must first recall that the international legal system is considered to be a system of states:⁷⁴ the settlement of disputes remains largely dependent on the consent of the states involved,⁷⁵ and the exercise of jurisdiction by international courts and tribunals is not integrated into an institutionalised and mandatory legal system as at the domestic level.⁷⁶ It must also be recalled that states have the upper hand by choosing whether to create a court in the first place, by deciding on the nature of the agreement that will institute a court or tribunal⁷⁷ and the substantive law which will apply⁷⁸ and, in most instances and particularly important here, by choosing to be a party to a case.

As a result, the first indisputable factor pointing to judicial activism would be a ruling that explicitly goes against the will of the parties and the principle of state consent. Ruling against the accepted law in force would be an example of this, but so too would be deciding against what states have previously explicitly accepted as the law, be it in treaties and conventions, statements, public opinions or judicial proceedings.⁷⁹ Next, and flowing from this first factor, judicial activism involves modifying the law from what it was previously accepted to be. The focus here would be on the legal rules or principles themselves and their amendment, as opposed to the will or the consent of the state. It could involve departing from previous interpretations of a principle that were already accepted as law in such a way as to create incoherence or uncertainty. These are all indications of a judge who is ‘making sense’⁸⁰ of new law, possibly due to dissatisfaction with existing law, the law which was, by and large, already recognised and accepted by that system of states. A third indication of activism, which is somewhat related to the former two, would consist in changing a judicial process or procedure in flagrant opposition to accepted customary practice.

Another characteristic of the international legal system, which leads to our next criterion, is the material incompleteness of international law.⁸¹ This is the presumption that international law, by its very nature, has not evolved or become detailed enough to be seen as a complete system of laws, rules or norms,⁸² thus leaving huge gaps in legal regulation. Despite this, legal certainty through judicial decisions is required. The act of deriving legal reasoning from abstract ideas or principles without any necessary legal certainty as to their true definition could reflect judicial activism but also restraint, as it might lead the judge to refrain from deciding.⁸³ However far-fetched they may be, judicial decisions are expected to ensure certainty, and coherent reasoning is needed to support the ultimate decision rendered. Equally, a clearly result-oriented decision, either lacking in judicial interpretation or pulling a rabbit out of its hat, can be a characteristic of both activism and restraint, since the result sought could indicate the mental state of the court in taking the decision and its intention to either expand or retract the law. Finally, refusing to interpret or expand upon a legal point raised by the parties or to even carry out any interpretation would be an indication of judicial restraint, as Lauterpacht and Kooijmans noted.

5 Recognition of the Indispensable Parties Principle

Although the indispensable parties principle has come to be accepted as a governing principle or conventional wisdom in international law, its true origins remain controversial.⁸⁴ The introduction of the principle in its current state occurred in the case of Monetary Gold, where the ICJ held that it ‘will not exercise its jurisdiction where the legal interests of a third State “would not only be affected by a decision, but would form the very subject-matter of the decision”’.⁸⁵ In its reasoning, the ICJ turned to the principle of consent to explain its rationale, holding that ‘to adjudicate … would run counter to a well-established principle of international law embodied in the Court’s statute, namely, that the Court can only exercise jurisdiction over a State with its consent’⁸⁶ In other words, the ICJ found that even in a duly constituted bilateral contentious case it would not have jurisdiction if it appeared that the principal issue to be decided affected a third state which was not a party to the proceedings.⁸⁷ Even though that third state would not be bound by the court’s decision,⁸⁸ it nevertheless considered that state’s interests with such regard that it was precluded from exercising jurisdiction.⁸⁹ Arguably, in its attempt to protect the interests of unaware third states, the ICJ assumed a function that sought to protect the interests of the general international community.

A closer look at the language used by the ICJ is required. This is because while the ICJ alluded to an interpretation of the ICJ Statute, a reading of both the text of the Statute and the decision do not evidence such a link. In fact, even the use of the word ‘embodied’ seems problematic. Firstly, the term is technically unclear⁹⁰ and lacks any legal meaning. Further, the fact that the ICJ Statute is silent with regard to third parties⁹¹ and their consent leaves it unclear as to where the court identified this principle so ‘embodied’. Notably, Article 36 of the ICJ Statute that deals with consent focuses on the consent of the ‘parties that refer the case to it’, not that of third states.⁹² Furthermore, a survey of other decisions from the same era fails to provide any indication as to the meaning of the word, even though the ICJ had proven itself capable of expanding upon legally unclear terms at the time.⁹³ Additionally, if the court meant to derive the Monetary Gold principle from the overarching principle of consent alone, it could have done so without the reference to the ICJ Statute and certainly without using the word ‘embodied’. Worthy to note, at this stage, is also the previous ICJ decision in the Corfu Channel case, where neither the court nor the parties seemed to have had any issue with addressing the dispute in the absence of a third state, Yugoslavia.⁹⁴

This ICJ’s ambiguous language, presented with little explanation and confined to one paragraph in a nineteen-page decision, provides little understanding as to the true source of the indispensable parties principle.⁹⁵ While the court used the words ‘principle of international law’, it certainly does not appear to be interpreting the issue of audi alteram partem, a general principle of law,⁹⁶ as it did not mention the case law of the Permanent Court of International Justice or other tribunals to support its reasoning.⁹⁷ In truth, the lack of justification by the court can only be interpreted as pure assertion, as pulling a rabbit out of its hat. In applying our judicial activism or judicial restraint criteria to this case, the situation gets even more complex. As already noted, a lack of justification is usually an indication of judicial restraint – something supported by Hersch Lauterpacht, who noted the ‘degree of caution’ with which the court decided this case.⁹⁸

The approach taken by the Court is also result-orientated, which supports a clear activist judgment. It introduced a new abstract principle, which it claimed it found in the Statute, but did so without legal certainty since the Statute itself is silent. It ultimately transformed the issues before it into a question of third-party legal interests and introduced the ‘essential parties’ concept, yet unclear as to where it applied it from, which could imply a change in judicial process of the court. On the one hand, the court created a principle of protection for states not parties to a dispute; on the other, it did so by ignoring the dispute before it, rendering an ineffective judgment.

The first case of interest to have followed Monetary Gold was Nicaragua,⁹⁹ where the indispensable parties principle was pleaded by one of the parties to the dispute as one of numerous grounds for objecting to the court’s jurisdiction.¹⁰⁰ In this instance, the court rejected the plea; dedicating a paragraph to the matter, it remarked that the ‘circumstances of the Monetary Gold case probably represent the limit of the power of the Court to refuse to exercise its jurisdiction’,¹⁰¹ making it necessary for the third party to be ‘truly indispensable to the pursuance of the proceedings’.¹⁰² One may wonder whether the wording ‘the limit of the power’ constitutes a reaffirmation of the principle of Monetary Gold¹⁰³ or rather reflects the discontent of the court, at the time, with the usefulness of this principle. Due to the lack of any reasoning, as an attempt to clarify the principle in substance, a restraint approach can be detected. However, considering the numerous other matters decided upon in the Nicaragua decision, the issue of the non-application of the Monetary Gold principle would seem inconsequential.

The principle was examined again in the case of Certain Phosphate Lands in Nauru.¹⁰⁴ Here, the ICJ held that while a decision in the case might have implications for a third party, ‘no finding in respect of that legal situation will be needed as a basis of the Court’s decision’.¹⁰⁵ This was in contrast to Monetary Gold, where determination of the legal interests of the third party would have been a prerequisite to decide upon the dispute.¹⁰⁶ In order to create a distinction, the court seems to have treated the issue in the Nauru case as one of degree of the possible implications for the third State,¹⁰⁷ expanding the principle of indispensable parties through an interpretation alone and without even having applied it, and despite the claim in Nicaragua that those were the limits of its application. This idea was clarified in the separate opinion of Judge Shahabuddeen, who noted that ‘the test is not merely one of sameness of subject-matter, but also one of whether … the Court is making a judicial determination of the responsibility of a non-party State’.¹⁰⁸ Here, there seems to be an allusion to the principle of consent, rather than an interpretation of the Statute as was alluded to in Monetary Gold, yet the court makes no such direct reference. In any event, a comparison of the facts of the two cases, Nauru and Monetary Gold, and their inherent similarities make it difficult to understand the resulting decision in each case.¹⁰⁹

The question that preoccupied the court seems to have been the intensity of the effect of the judgment on the legal interests of an absent state.¹¹⁰ This shows a court attempting to translate Nicaragua’s allusions to ‘appropriate circumstances’ and ‘limits’ into a more judicially administrable test,¹¹¹ as suggested by Judge Shahabuddeen’s explanation. Accordingly, it would seem that the court borrowed its reasoning from domestic law,¹¹² possibly through normative deduction,¹¹³ by introducing a form of joint and several responsibility into the reasoning of international law: while the breach was committed jointly by different states, it does not preclude the admissibility of the claim against one of those responsible actors.¹¹⁴ This is arguably to protect the public function the court wishes to fulfil. The court’s judgment is an analysis, not of the ICJ Statute but instead of the practice of the court’s previous decision, an indication that it was interpreting its very own practice to reach a conclusion in the present case.

In considering the activism or restraint criteria, we can see this as a clearly result-oriented decision through borrowing principles from other legal systems, which indicates a proactive tendency on the part of the court. Arguably, in ‘clarifying’ the principle, the court seems to have caused, nevertheless, further confusion as to when the indispensable parties principle is applied, opening the door to future inconsistency, which can possibly imply a modification of the law or the procedure in question. This is furthered through the four dissenting opinions to the judgment, including both the president and the vice-president of the ICJ at the time,¹¹⁵ one of whom noted that ‘the protection afforded the absent States by Article 59 in the quite exceptional situation of this case would be notional rather than real’.¹¹⁶

Despite its activism, the Nauru case failed to establish an ‘administrable test’ for the principle,¹¹⁷ as became evident in the case of East Timor,¹¹⁸ where the ICJ attempted to build on its Monetary Gold analysis by changing the narrative yet again. In contrast to the treatment of the matter as one of degree seen in the Nauru case, the case of East Timor considered a temporal precondition instead¹¹⁹ – namely, by holding that it would first have to decide on that third state’s actions (or inactions), it could ‘not make such a determination in the absence of the consent of [the third party]’.¹²⁰ In determining that the treaty-making capacity of the third, absent, state would form an integral part of its decision, it effectively put a stop to the trend of rejecting the Monetary Gold principle. It ultimately delivered a narrow interpretation of the Monetary Gold principle, without any reasoning as to why it considered the issue in temporal terms rather than as a matter of degree.¹²¹

This is clearly a result-oriented approach, whereby the decision itself can be regarded as a decision not to decide, turning the reasoning back to one of assertion. Although the court did engage in some analysis of the submissions of the parties, it rejected them without providing an explanation. It based its rejection on consent rather than on the ICJ Statute, which indicates an interpretation of an unwritten principle (though without any clear indications from the court, this remains speculation on the part of the present author). This case drew reactions from within the court in the form of two dissenting opinions,¹²² which brought up the unresolved issue of the erga omnes nature of the subject matter.¹²³ By again modifying the process whereby the indispensable parties principle is identified, the ICJ went around its Nauru decision and returned to Monetary Gold, which resulted in greater lack of coherence regarding the principle.¹²⁴ The refusal of the court to decide on erga omnes rights, which involve a public concern, leaves questions as to the role of the court in this matter.¹²⁵ The principle was used to limit the possible public function the ICJ could have assumed as the principal judicial organ of the UN,¹²⁶ considering its widespread jurisdictional powers.¹²⁷ Τhe court furthermore elaborated the principle abstractly and without any legal certainty, which was a further indication of the restraint with which it acted. The lack of interpretation and any indication as to the source of the temporal element increased the already existing ambiguity over when the Monetary Gold principle applies or does not apply. Finally, this refusal to rule on a highly controversial matter shows judicial restraint par excellence.

6 Indispensable Parties and Other International Tribunals

6.1 The Principle Applied

As we have seen, one measure of judicial effectiveness is to consider whether the decisions of international courts are harmonised at a systemic level, meaning that principles of law accepted and endorsed by some courts become accepted as applying to other judicial institutions across the international stage. Telling, in this regard, are the decisions concerning the indispensable parties principle before other tribunals and courts.

Notable is the case of Larsen v. Hawaiian Kingdom,¹²⁸ which is the only case in which the principle was applied in such a manner as to prevent an international tribunal from exercising its jurisdiction.¹²⁹ The arbitral tribunal, constituted under the auspices of the Permanent Court of Arbitration (PCA), ultimately dismissed the case for lack of authority to ‘exercise jurisdiction over a State unless that State has given its consent to that jurisdiction’.¹³⁰ It upheld this test because the tribunal ‘operates within the general confines of public international law’,¹³¹ thus extending the application of the principle beyond the ICJ’s mandate and beyond what the ICJ had pronounced on the principle. The tribunal can be said to have added to the definition of the Monetary Gold case, going beyond what the ICJ had previously considered to be a matter of the ICJ Statute, in a hint of judicial activism. Another possible consideration to take into account here is the fact that the parties’ real motive may have not been to resolve the dispute between them but rather to raise publicity for the cause of the Hawaiian nationalist movement by having the tribunal render an opinion on the legal status of Hawaii.¹³² The tribunal’s choice to uphold the principle may have been heavily influenced by the need to reject the case in any way possible.

The indispensable parties principle was also raised in the South China Sea Arbitration (Philippines/China),¹³³ where an intervening third state, Malaysia, asked the tribunal to reject jurisdiction on the basis that it might affect its rights and obligations as an absent third state. Without providing any explanation beyond the decision of the ICJ in Nicaragua, the tribunal took the view that Malaysia ‘overstated’ the Monetary Gold principle, as the ‘more expansive reading would impermissibly constrain the practical ability of courts and tribunals to carry out their function’.¹³⁴ Remarkably, in contrast to the narrow interpretation the ICJ applied in East Timor, this tribunal saw an expansive reading as limiting the judicial function. Clarifying that the relevant issues in the case concerned ‘areas to which Malaysia makes no claim’,¹³⁵ it held the latter’s interests were not affected. Interestingly, the difference in reasoning between the ICJ’s shaping of the rule as we know it today and the tribunal’s approach to is suggestive of activism, leading to dis-harmonisation and, by consequence, ambiguity.

Mention must also be made of the M/V Norstar case before the International Tribunal for the Law of the Sea (ITLOS),¹³⁶ where the tribunal ‘acknowledge[d] that the notion of indispensable party is a well-established procedural rule in international judicial proceedings’.¹³⁷ It nevertheless refrained from applying the principle in that specific case,¹³⁸ leaving an unexplained reference to the principle, insufficient for deeper examination.

6.2 Lack of Relevance of the Principle

Although the indispensable parties principle has, by and large, been accepted as well established, the role of the ICJ in creating a new rule of law remains questionable, as its role as a rather reluctant lawmaker arises. This is particularly pertinent when one considers that certain other international courts have rejected the relevance of the principle. In this vein, we can see the complete rejection of the principle in the opinion of Advocate General Wathelet in the Western Sahara Campaign v. United Kingdom¹³⁹case before the Court of Justice of the European Union (CJEU), who rejected its application as it would allegedly automatically preclude the possible examination or review of international agreements between the EU and third states.¹⁴⁰ The Advocate General’s lack of analysis suggests that he was exercising judicial restraint. Prior to that, a World Trade Organization (WTO) panel also held that there is no concept of ‘essential parties’ in WTO law,¹⁴¹ despite examining the case law of the ICJ and using it as evidence to elaborate on the content of the principle.¹⁴² Most recently, in 2021, the International Criminal Court refused to apply the principle when requested, on the grounds that its jurisdiction did not concern inter-state disputes but dealt instead with natural persons.¹⁴³ Without a doubt, these decisions indicate the failure of the Monetary Gold principle to achieve support within the international judicial community both in terms of fostering harmonisation and as a new rule of international law.

The European Court of Human Rights (the ECtHR) has also taken a differentiated approach to this principle. In the case of Bankovic¹⁴⁴ the ECtHR ruled out any need to decide on an objection raised that was based explicitly on the Monetary Gold principle¹⁴⁵ as it declined jurisdiction over other issues in the case that apparently took precedence over any rights deriving from the absent third state principle. Similarly and maybe particularly tellingly is the fact that the same court has had no difficulty providing detailed consideration of the conduct of states not parties to its proceedings or sometimes not even members of the Council of Europe.¹⁴⁶ This, for instance, occurred when the facts of the case pointed to a possible violation of the Convention, as most famously occurred in Soering,¹⁴⁷ where the court decided against the extradition of the applicant to a third state because it was quite possible that that absent third state would violate the Convention. Interestingly, the question of the essential third party was not even raised, despite the court having explicitly taken decisions in that regard. It is thus evident that this was a result-oriented decision made with the intention of solidifying the law and as such is indicative of judicial activism.

7 Effectiveness or Ambiguity?

7.1 Consolidation of the Indispensable Parties Principle

As seen in the Introduction, the interaction between the use of certain principles of customary international law and judicial activism can yield an uncomfortable relationship. This is one where the inherent tension between custom’s recognition of unwritten law through the identification of state practice and opinio juris and judicial activism’s ‘creative reasoning rather than strict application of the law’ seek to co-exist.¹⁴⁸ An analysis of whether the indispensable parties principle as identified in Monetary Gold qualifies as custom lies outside the confines of the present discussion. However, it is interesting to note the overlap between custom and activism in the judicial process that enables the principle to be characterised as one of customary law. Although the principle had appeared in international decisions prior to Monetary Gold, the ICJ seems to have pulled a rabbit out of its hat when applying it in that case. The existence of prior references to the rule, of which the court made no mention, makes its approach a form of continuity in the judicial interpretation of this principle rather than a new apparition altogether. However, its vague terminology left the source of the rule open¹⁴⁹ and gave way to its subsequent evolution – a clear lack of coherence and consistency in the decision.

Additionally, it cannot be denied that, despite not having been applied by tribunals, the rule has been relied on repeatedly by states, which indicates its acceptance as law and in practice.¹⁵⁰ Indeed, it has also been argued that the lack of objections to a string of judicial decisions may signify support for a positive customary rule.¹⁵¹ What this analysis has shown is a judicial process of thought which, through activism and restraint, has been able to create what can best be described as a principle of customary procedural law.

7.2 The Judicial Function and the Indispensable Parties Principle

Returning to the effectiveness or ambiguity of international courts in the application of the indispensable parties principle, and since its re-introduction in international legal discourse through the Monetary Gold case, there are several observations that can be made.

There is a very important distinction that need to be drawn between, on one hand, the cases where the principle was applied, and, on the other, the cases where the principle was recognised but not applied. In Monetary Gold we saw that the ICJ sought to uphold an indisputable public function, which was to protect the interests of third states not parties to the proceedings. It did so, even if this meant rejecting the entire case and despite the parties having consented to its jurisdiction. We must also consider the utility of leaving dispute unaddressed. A case in point is East Timor, where questions of erga omnes and self-determination arose. As former ICJ judge Kooijmans established, restraint is reflected in instances where the court refuses to decide on a matter which is highly controversial, as happened in this case. The ICJ did not even attempt to provide an answer to these long-standing questions, which would have benefitted the international legal scene – something it was perfectly qualified to do, given its wide jurisdictional powers. Even though reference was made to Article 59 of the ICJ Statute, according to which the decision would be binding only upon the states parties to the proceedings, the ICJ was nonetheless unwilling to decide upon the legal interests of any third state. The refusal to decide was clearly a policy decision, as it was also for the PCA tribunal in Larsen, where a decision would have promoted the wrong political gains.

By contrast, and quite interestingly, we can also see a public function in deciding on the dispute, as was apparent in Nicaragua and Certain Phosphates of Nauru, so much so that in this latter case the court considered that even though other states could also be held liable, it was sufficient that liability arose for that one state party alone. This was an interesting reasoning, outside the bounds of what had been previously accepted. Notable also are the approaches taken in other courts. Advocate General Wathelet’s comment in Western Sahara was indicative of the very bounds of the principle, yet also demonstrates the restraint implicit in a refusal to decide. What if a dispute arising out of a convention with a third party only affects the legal interests of a member state of the EU? Similarly, the rejection of the principle in the South China Sea arbitration and by the ECtHR in Bankovic show a public function quite different from the one assumed by the ICJ in those two cases in accepting the indispensable party principle. In truth, we can see how the reasoning of the tribunals alluded to greater public benefit in deciding rather than not deciding the cases.

As already observed, judicial effectiveness also calls for systemic harmonisation at the international level – something the indispensable party principle also fails to meet. If there is any consistency in the decisions examined, it ironically lies in their disharmony, for the manner in which the principle is applied, whether within a single court or across several courts. This is evidenced, for example, in the lack of coherent or continuous reasoning across the decisions of the ICJ. At the same time the principle was openly accepted by most international courts and tribunals as an established rule of international law, despite not being applied. If we come back to the utility of the principle and its effectiveness at the international level, the lack of its use could be indicatory of its lack of any effectiveness. If the idea is to create a form of ‘transnational public order’¹⁵² whereby all the courts and tribunals share a set of principles, even at the procedural level, creating predictability and coherence at the international level, then the indispensable party rule certainly does not meet this standard.

Turning finally to the judge’s role as reluctant lawmaker, the question arises as to whether, in adjudicating Monetary Gold, or even East Timor, the ICJ has made law. The wording of the Monetary Gold judgment alludes to a principle already accepted in international law – something that could be reflected in previous decisions of international courts and tribunals, as seen above, despite the fact that the court did not mention any. Conceivably, the principle may have existed as one of custom, without further substance as to its content. Going beyond the acceptance of the principle, whatever its source might be, subsequent ICJ cases attempted to create a methodology through which this principle would be applicable. However, this methodology, or ‘law’, has been rejected repeatedly by other international courts and on most occasions by the ICJ itself. This is where the question of methodology in custom becomes even more important: does the occasional recognition, but not application, of a rule, make law?

8 Conclusion

Coming back to the use activism and restraint to drive customary international law forward to yield effectiveness, there are numerous questions posed within this analysis in that regard. Going back to the elements of the judicial function, the preceding paragraph has indicated the very inability of the Monetary Gold principle to create judicial effectiveness.¹⁵³ Instead, what can be seen is ambiguity, lack of coherence and a clear rejection of the principle by several courts.

The lack of certainty over both the source and true application of the indispensable third party principle leaves much to be desired. The ICJ’s assertion that the principle exists as embodied in the ICJ Statute and the subsequent recognition and evolution of its methodology raise questions about the relationship between customary norms and the use of activism to identify them. The lack of judicial reasoning points to the principle being used to avoid larger questions of law raised by the facts of a particular case. Such reticence is by and large an ingredient of judicial ambiguity and ineffectiveness. Although effectiveness may arguably have made an appearance in the original Monetary Gold case, depending on one’s perspective it appears to have been short-lived.

In conclusion, while a clear answer certainly cannot be provided through the examination of just one principle, the use of mere assertion, often under the guise of CIL, certainly alludes to the use of custom as a tool by which judicial activism manifests itself in excess.

9 Judicial Dialogue between International Courts in the Interpretation of Customary International Human Rights Law

Silviana Cocan

1 Introduction

The identification and interpretation of customary international law (CIL) by both domestic and international courts and tribunals has been thoroughly studied in legal scholarship. However, little is known about the engagement in judicial dialogue by, in particular, international human rights courts and the impact that it has on the interpretation of custom in this particular field. In the international legal order, international bodies protecting human rights were conceived to be formally independent, in contrast with domestic tribunals governed by a hierarchical principle of organisation. Indeed, except for the International Court of Justice (ICJ), which has general jurisdiction in matters related to international law, international courts exercise limited jurisdiction, usually determined by a constitutive treaty. Many judicial and quasi-judicial bodies co-exist independently of each other across the many legal systems that protect human rights, be it globally or at regional level. Despite the horizontality of this ordering, judicial dialogue has emerged as a spontaneous practice in the case law of international courts, part of a larger judicial globalization phenomenon. Judicial globalization involves interacting judicially ‘across, above and below borders, exchanging ideas and cooperating in cases involving national as much international law’.¹ Although judicial globalization is becoming more common, binding precedent still does not exist in the international legal order,² rather, judicial dialogue has arisen within the context of the jurisdictionalisation of international human rights law at both domestic and international levels.

There is no universal agreement on the meaning of judicial dialogue. Judicial dialogue can be defined as merely the spontaneous reference to the case law of other courts and tribunals by a particular judicial body, whether domestic or international. It can be described also as a comparative and interpretative approach to cross-cutting issues faced by multiple legal systems – this is the case with the protection of human rights. Indeed, judicial dialogue can be understood as a practice engaged in spontaneously by courts, either in a sporadic fashion through occasional references to the case law of other courts or as part of a more systematic approach in which references to foreign case law are used repeatedly and consistently over time in the process of interpretation. For the purpose of this contribution, the notion of judicial dialogue encompasses the notion of cross-referencing,³ These terms are used interchangeably to describe the reference to case law or international instruments that are outside the international court’s own judicial system and that are used for interpretation purposes.⁴

References to international instruments and to other courts’ case law are often intertwined, as the interpreter tends first to contextualise the legal norms within the broader system of analogous rules that are part of other systems, then afterwards refers to or quotes extensively the relevant case law which interprets the analogous rules. Therefore, the practice of judicial dialogue leads to a contextualization of rules within the international legal order as a whole and the taking account of judicial practice and the interpretation given by other courts to analogous rules in the field of international human rights law. Firstly, it sets out the basis for a normative contextualisation, interpreting legal rules protecting human rights within the broader context of international instruments such as treaties, customs, soft law documents and general principles of international law. Secondly, it facilitates systemic contextualisation in the process of interpreting human rights obligations through the overall logic and perspective of the universal and regional systems while taking into account their common coherence and scope based on the universality of human rights in spite of each legal system’s independence. On the one hand, judicial dialogue is a tool for normative contextualisation of rules protecting human rights, whether written or unwritten, according to the interpretation of their scope and content given by other international bodies in comparable legal matters. On the other hand, the practice of judicial dialogue reflects the search for a systemic contextualisation that would anchor the interpretation process in the light of other analogous systems – as all the systems protecting human rights in the international legal order have a common purpose based on an overarching principle that is the limitation of state power through the promotion and the protection of rights inherent to all human beings, without discrimination.

When the interpreter sets out the basis for normative and systemic contextualisation by taking into account external references when engaging in the interpretation process, the approach follows the following steps: (1) the interpreter compares two analogous rules and realises that other judicial bodies have interpreted the same rules in other legal disputes; (2) this comparative approach leads the interpreter to take into account in the interpretation process the general coherence of the foreign system protecting human rights; (3) the interpreter evaluates if references to the rules and the case law established in this analogous system outside the interpreter’s own judicial system could be relevant – according to principles, rules and methods commonly admitted in that particular system; and finally (4) the interpreter possibly decides to incorporate external elements such as judicial decisions of other systems if they meet the objective of the interpreter’s legal reasoning, which is subject to constraints imposed by the interpreter’s own system. Given all this, the belief that fragmentation negatively affects international law is perhaps exaggerated, at least insofar as international human rights law is concerned. Indeed, the aim of universality and the interdependent character of the rights affirmed in the Universal Declaration of Human Rights in 1948,⁵ leads one to think that the universal and regional systems protecting human rights are more likely to have practices in common and intersections, making combinative and overarching interpretations not only possible but inevitable.⁶

Section 2 discusses the role of judicial dialogue in the identification and the interpretation of customary international human rights law. It highlights how customary rules of human rights law arise through the practice of international courts as they interpret written provisions codified in universal or regional instruments while taking into account other courts’ case law. Section 3 addresses the issue of judicial dialogue as an interpretation approach that ensures judicial objectivity and judicial dialogue’s impact on customary international human rights law. In conclusion, Section 4 provides a forward-looking analysis of how judicial dialogue may play a role in ensuring a higher degree of normative convergence on cross-cutting issues in the protection of human rights.

2 The Use of Judicial Dialogue in the Identification and the Interpretation of Customary International Human Rights Law

In the field of international human rights law, the identification and interpretation of customary rules are often interlinked. International courts interpret international instruments, state practice and opinio juris in order to ascertain whether there exists a general rule belonging to customary international law alongside the written rule codified in a treaty. For instance, judicial dialogue has been used as a tool in the identification and interpretation of jus cogens norms protecting human rights, such as the prohibition of torture, which is also part of CIL. By engaging in judicial dialogue, judges have taken into account the case law of other courts to identify customary rules crystallised through the practice of international bodies. This process allowed the judges to conclude that the binding nature of provisional measures has become a common practice across many systems of human rights protection.

2.1 Blurred Lines between the Identification and the Interpretation of Customary International Human Rights Law

2.1.1 General Considerations on the Identification and the Interpretation of Customary Rules

A distinction is not always clearly drawn in human rights case law between the recognition of a written norm as customary and its judicial interpretation. If the rule is codified in a treaty that is the source of the judicial body’s jurisdiction, the existence of the rule is not in question, and yet the rule needs to be interpreted before it is applied to a specific factual situation. If we are in the presence of an unwritten norm that might be considered customary international human rights law, the judicial body establishes, at a precise moment, that a rule has become customary because of widespread ratification of relevant international instruments, state practice and opinio juris while also taking into account other relevant materials such as case law, soft law instruments, resolutions, reports of international institutions and legal doctrine. Through this process, the rule is identified as being part of customary law and binding on states without prior or explicit consent. Within this framework, international courts not only evaluate state practice and opinio juris in identifying a customary rule, but very often include references to fundamental values, considerations of humanity and the case law of other courts, whether domestic or international, so as to clarify the content and the scope of international obligations.

The International Law Commission (ILC) highlighted in its 2018 report on the identification of customary international law⁷ that it is necessary to ascertain the presence of two elements: state practice and opinio juris. The report includes an assessment of evidence indicative of each element.⁸ The ILC examined state conduct and state practice in order to determine the existence of a customary rule⁹. It has also stated that ‘[d]ecisions of international courts and tribunals, in particular of the International Court of Justice, concerning the existence and content of rules of customary international law are a subsidiary means for the determination of such rules’.¹⁰ The ILC pointed out that the process of determining the existence and content of customary rules could also take into account decisions of national courts, but that they would have a less important role, depending on the context.¹¹

This acknowledgement on the identification of customary rules has specific implications in the field of human rights. Indeed, the practice of international tribunals and the emergence of customary international human rights law mark a reversal of the logic informing the process of identifying customary rules. In contrast to other fields of international law, in which customary law appeared first and was codified afterwards in binding treaties, ‘in international human rights law, custom did not precede treaty, it followed it’.¹² Consequently, normative convergence in the practice of human rights bodies may lead to cross-cutting rules that are common to all the systems, whether at universal or regional level, and which could also be part of positive law in domestic legal orders. It can reveal the substantive interdependence of international obligations laid down in the case law of international courts to protect human rights. The way in which the courts’ case law and interpretative statements have contributed to the process of identifying customary rules can be illustrated by considering the scope and content of peremptory norms.

2.1.2 The Intersection between the Identification and the Interpretation of Human Rights and Jus Cogens Norms

Although Article 53 of the Vienna Convention on the Law of Treaties¹³ (VCLT) clarified what is meant by jus cogens norms in international law, no concrete examples were given of these norms, leaving it up to international bodies to define what these norms are. For instance, in 1994, in its General Comment 24, the Human Rights Committee observed: ‘Reservations that offend peremptory norms would not be compatible with the object and purpose of the Covenant. Although treaties that are mere exchanges of obligations between States allow them to reserve inter se application of rules of general international law, it is otherwise in human rights treaties, which are for the benefit of persons within their jurisdiction.’¹⁴ In the Committee’s view, ‘provisions in the Covenant that represent customary international law (and a fortiori when they have the character of peremptory norms) may not be the subject of reservations.’¹⁵ The Human Rights Committee lists the customary rules found in the Covenant as follows:

Accordingly, a State may not reserve the right to engage in slavery, to torture, to subject persons to cruel, inhuman or degrading treatment or punishment, to arbitrarily deprive persons of their lives, to arbitrarily arrest and detain persons, to deny freedom of thought, conscience and religion, to presume a person guilty unless he proves his innocence, to execute pregnant women or children, to permit the advocacy of national, racial or religious hatred, to deny to persons of marriageable age the right to marry, or to deny to minorities the right to enjoy their own culture, profess their own religion, or use their own language. And while reservations to particular clauses of Article 14 may be acceptable, a general reservation to the right to a fair trial would not be.¹⁶

However, in its subsequent general comments, the Human Rights Committee did not restate this conclusion nor renew this affirmation concerning customary rules that cannot be subject to any reservations. Furthermore, no other human rights body has made a similar statement declaring all these human rights to be jus cogens. Therefore, it is difficult to identify with certainty the customary rules of human rights that are both part of positive law, alongside conventional provisions, and have a peremptory character.

In this context, identification and interpretation of customary rules can be seen as ‘interconnected judicial operations’¹⁷ that are explicitly differentiated throughout the process of legal reasoning. As international courts refer to customary rules in their case law, there is indeed a ‘distinction between customary norms and State practice with opinio juris’.¹⁸ In scholarship it has been pointed out that, when applied to treaty law, ‘interpretation and identification are two separate processes’; whereas ‘with regard to customary rules, since they are unwritten, it is difficult to distinguish their identification from their interpretation’.¹⁹ Moreover, the existence of customary international law ‘is determined inductively through an examination of two elements, state practice and opinio juris’.²⁰ In other words, a state practice must implicitly be interpreted as being general and repeated throughout time and this general practice must be accepted as law in accordance with Article 38(1)(d) of the Statute of the International Court of Justice.²¹ Once customary rules have been identified, they can, like treaties, also be subjected to interpretation, their unwritten nature allowing a more flexible interpretation where their content is uncertain or vague. As pointed out by Judge Tanaka

Customary law, being vague and containing gaps compared with written law, requires precision and completion about its content. This task, in its nature being interpretative, would be incumbent upon the Court. The method of logical and teleological interpretation can be applied in the case of customary law as in the case of written law.²²

This statement allows us to reach the conclusion that not only are unwritten customary rules open to interpretation so as to become fully applicable to a particular matter, but also that the process of interpretation can follow a teleological approach informed by the object and purpose of the rule. When the customary rule’s object and purpose is to protect human dignity and integrity by constraining states in their behaviour, an extensive interpretation would be one that leads to a broadening of the content of state obligations in order to enhance the protection of the individual. On the other hand, a restrictive interpretation would tend to limit the scope of application of legal rules by giving much weight to State practice and explicit consent.

2.2 Judicial Dialogue as a Tool in the Identification and Interpretation of Jus Cogens Norms Protecting Human Rights

The ILC’s special rapporteur Dire Tladi recalled that if ‘a State has objected to a rule of customary international law while that rule was in the process of formation, the rule is not opposable to the State concerned for so long as it maintains its objection’.²³ However, the ILC emphasised that ‘the persistent objector rule does not apply to peremptory norms of general international law (jus cogens)’.²⁴ This conclusion ‘flows from both the universal application and hierarchical superiority of [these norms] … that apply to all States’.²⁵ In its 2019 report on the peremptory norms of general international law, the ILC affirmed that ‘[c]ustomary international law is the most common basis for peremptory norms of general international law (jus cogens)’.²⁶ adding that ‘[t]reaty provisions and general principles of law may also serve as bases for peremptory norms of general international law (jus cogens)’.²⁷ It also observed that ‘[d]ecisions of international courts and tribunals, in particular of the International Court of Justice, are a subsidiary means for determining the peremptory character of norms of general international law’,²⁸ as is the case with the determination of CIL. In the ILC’s 2022 report Dire Tladi provided the most recent list of norms considered to be part of jus cogens and which reflect fundamental values for the international community as a whole. They include the prohibition of aggression; the prohibition of genocide; the prohibition of crimes against humanity; the basic rules of international humanitarian law; the prohibition of racial discrimination and apartheid; the prohibition of slavery; the prohibition of torture; and the right of self-determination.²⁹ It is interesting to note that this list partially overlaps with customary rules identified as such in legal scholarship, examples of which are ‘the prohibition of genocide and torture, the prohibition of slavery and piracy, the rules on State responsibility, the principle of non-refoulement and the no-harm rule’.³⁰

In Conclusion 14, the special rapporteur pointed out that ‘[a] rule of customary international law not of a peremptory character ceases to exist if and to the extent that it conflicts with a new peremptory norm of general international law (jus cogens)’.³¹ This statement could be relevant in future cases dealing with the relationship between legal norms that are not at an equivalent hierarchical level. It could determine the effect of a jus cogens norm when there is a conflict with a customary rule, such as the normative interaction between the prohibition of torture and the rule on state immunity before foreign jurisdictions. An extensive interpretation of Conclusion 14 would lead to neutralisation of the CIL immunity rule’s precedence over the peremptory norm when the application of the first rule renders ineffective in its scope the customary rule that has jus cogens status. However, for that to be the case, one must first consider that there is an existing conflict between, on the one hand, international customary law on immunities and, on the other, erga omnes obligations and jus cogens norms. The main uncertainty lies in the relationship between customary rules related to state immunities and the hierarchical character of jus cogens norms that should entail effective legal consequences. The ILC’s special rapporteur stated:

The hierarchical superiority of peremptory norms of general international law (jus cogens) over customary international law was … recognized in Al-Adsani v. the United Kingdom,^[32] in which the European Court of Human Rights (ECtHR) determined, having considered Prosecutor v. Furundžija,^[33] that peremptory norms of general international law (jus cogens) are those norms that enjoy ‘a higher rank in the international hierarchy than treaty law and even “ordinary” customary rules’.³⁴

The ECtHR affirmed that ‘the right under Article 3 not to be subjected to torture or to inhuman or degrading treatment or punishment enshrines one of the fundamental values of democratic society’ and that ‘[i]t is an absolute right, permitting of no exception in any circumstances’.³⁵ If the special rapporteur was indeed recalling the well-established case law of the European Court, it could have been criticised for its contradictions and limited legal consequences in terms of state accountability.

This precedent established by the ECtHR has led to a legal loophole in the case of grave human rights violations that occur extraterritorially and implicate a foreign state. Even in such exceptional circumstances, the customary law on immunities exercises a constraining effect on the legal consequences in terms of state responsibility, as individuals will have no access to justice. Indeed, as affirmed by the ECtHR itself:

Notwithstanding the special character of the prohibition of torture in international law, the Court is] unable to discern in the international instruments, judicial authorities or other materials before it any firm basis for concluding that, as a matter of international law, a State no longer enjoys immunity from civil suit in the courts of another State where acts of torture are alleged.³⁶

The dissent of Judges Rozakis and Caflisch from the Al-Adsani v. the United Kingdom solution, which was adopted by only nine votes in favour and eight against, showed the division among the judges at the time. The following words in the dissenting opinion show that the adoption of a radically different interpretation could have been possible:

By accepting that the rule on prohibition of torture is a rule of jus cogens, the majority recognise that it is hierarchically higher than any other rule of international law … For the basic characteristic of a jus cogens rule is that … it overrides any other rule which does not have the same status. In the event of a conflict between a jus cogens rule and any other rule of international law, the former prevails.³⁷

On the one hand, the ICJ followed the ECtHR’s precedent and ruled in its Jurisdictional Immunities of the State case³⁸ that there was no conflict between the rule on state immunities in civil proceedings and jus cogens norms, as the former is of a procedural nature while the latter are of a substantive nature. This case dealt with both a debate around the identification of an exception to state immunities where there are violations of jus cogens norms, as affirmed by the Italian Supreme Court in its Ferrini case,³⁹ and the resolution of a possible conflict of norms between the customary rule on immunities and the absolute prohibition of torture. An analysis of domestic and international case law led the ICJ to reject any exception to the regime of state immunity from foreign jurisdiction, even in the case of violations of peremptory norms. As a result of this restrictive interpretation, the prohibition on torture becomes devoid of substance in an extraterritorial context: its peremptory nature is illusory and impracticable, its legal effects and effective sanctions existing only in a theoretical imaginary, given that state immunity prevails as a sine qua non prior to any judicial proceedings.

On the other hand, with regard to peremptory norms, the case law of other international courts and tribunals has also been used to identify the emergence of customary international legal rules determined by other courts that are binding on all states and not limited in their application. In the Furundžija case, the Trial Chamber of the International Criminal Tribunal for the Former Yugoslavia (ICTY) found that the prohibition of torture had not only become part of customary international law but had also reached the status of a jus cogens norm.⁴⁰ The ICTY has also stated that the prohibition of rape within the context of an armed conflict had become a rule of customary international law despite the lack of a universal definition of rape in international law,⁴¹ the tribunal using the principle of the protection of human dignity to define the act of rape after analysing contradictory national legislations.⁴² The tribunal also defined the criteria of torture in armed conflict after recalling that ‘[t]he broad convergence of … international instruments and international jurisprudence demonstrates that there is now general acceptance of the main elements contained in the definition set out in article 1 of the Torture Convention’,⁴³ applicable in times of both peace and armed conflict.

It is also interesting to note that when the case law of international tribunals refers to the prohibition of torture as a customary norm that is part of jus cogens, the formula used is usually ‘prohibition of torture’ and not the universal treaty’s broader wording, which reads ‘the prohibition of torture and other cruel, inhuman or degrading treatment or punishment’.⁴⁴ Therefore, it is not clearly stated whether the proscription of inhuman or degrading treatment characterised by a minor gravity as compared with torture also fall under customary international law and could be qualified as a peremptory norm. For instance, in Questions Relating to the Obligation to Prosecute or Extradite case the ICJ stated that:

the prohibition of torture is part of customary international law and it has become a peremptory norm (jus cogens).

That prohibition is grounded in a widespread international practice and on the opinio juris of States. It appears in numerous international instruments of universal application (in particular the Universal Declaration of Human Rights of 1948, the 1949 Geneva Conventions for the protection of war victims; the International Covenant on Civil and Political Rights of 1966 ; General Assembly resolution 3452/30 of 9 December 1975 on the Protection of All Persons from Being Subjected to Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment), and it has been introduced into the domestic law of almost all States; finally, acts of torture are regularly denounced within national and international fora.⁴⁵

The court recalled that although Article 4 of the Convention against Torture requires states parties to criminalise such acts, ‘the obligation to prosecute the alleged perpetrators of acts of torture under the Convention applies only to facts having occurred after its entry into force for the State concerned’.⁴⁶ Nevertheless, it is not clear whether only the prohibition of torture is part of customary international law as a jus cogens norm or whether this prohibition necessarily also entails procedural obligations strongly linked to the effectiveness of the prohibition as a customary norm. Furthermore, as regards the Convention against Torture, the definition of acts of torture is strongly linked to states obligations as it requires involvement of a public official, whereas this is not the case with torture defined as a crime against humanity involving the liability of individuals.⁴⁷

Finally, in the Prosecutor v. Furundžija case, the ICTY analysed treaty provisions of international humanitarian law and human rights law,⁴⁸ recognised the numerous states parties to those treaties and, acknowledging that ‘torture in time of armed conflict is prohibited by a general rule of international law’, observed that ‘[i]n armed conflicts this rule may be applied both as part of international customary law and – if the requisite conditions are met – qua treaty law, the content of the prohibition being the same’.⁴⁹ With respect to the content of the prohibition of torture under conventional and customary international law, the tribunal remarked that states had the obligation not only to prohibit and punish torture but also to prevent any potential breaches of the prohibition of torture as well as any inhuman or degrading treatment, as had been ‘authoritatively held by the European Court of Human Rights’⁵⁰ in the Soering case.⁵¹ The ICTY concluded that ‘international rules prohibit not only torture but also (i) the failure to adopt the national measures necessary for implementing the prohibition and (ii) the maintenance in force or passage of laws which are contrary to the prohibition’.⁵² This conclusion is reinforced by the jus cogens nature of the prohibition of torture and the fact that it imposes erga omnes obligations designed to produce a ‘deterrent effect’.⁵³ For the tribunal, the peremptory character of the prohibition of torture has effects at the inter-state level, such as de-legitimising any legislative, administrative or judicial act authorising torture,⁵⁴ and at the individual level, enabling every state ‘to investigate, prosecute and punish or extradite individuals accused of torture, who are present in a territory under its jurisdiction’.⁵⁵

Analyses of the international case law related to the prohibition of torture have shown that its customary nature and content flow from the coherence of general principles of international law and treaty provisions applicable in international humanitarian and human rights law, analysed in the light of the international courts’ case law. It also appears that the customary prohibition of torture has distinct content and scope, binding all states as a peremptory norm of international law and giving rise to erga omnes obligations.

2.3 Cross-References and the Crystallisation of a New Customary Rule: The Example of the Binding Nature of Provisional Measures

Consideration of other international instruments and the associated case law resulting from their interpretation by other courts can also lead to the identification of new customary rules, as exemplified by the binding nature of provisional measures. In the case of Mamatkoulov and Askarov v. Turkey before the ECtHR, the applicants alleged that their extradition to Uzbekistan by the Turkish authorities exposed them to a real risk of ill-treatment proscribed by Article 3 of the European Convention on Human Rights (ECHR). The court had indicated an interim measure in application of Rule 39 of its Rules of Court. The provisional measure requested a suspension of the extradition proceedings for the purpose of establishing whether the risk of ill-treatment existed. Turkey’s failure to comply with the measure indicated by the Court raised the issue of the mandatory nature of interim measures and whether there was a breach of the effective exercise of the right of individual application guaranteed by Article 34 of the ECHR.

The LaGrand case⁵⁶ before the ICJ dealt with a dispute related to alleged violations of the Vienna Convention on Consular Relations of 24 April 1963 on the grounds that the applicants had been tried and sentenced to death without having been informed of their rights, as required under Article 36(1)(b) of the Vienna Convention. The ICJ indicated provisional measures, calling upon the United States to suspend the execution of the death penalty, but the respondent state failed to comply with the court’s order made under Article 41 of the ICJ Statute. The court had therefore to determine whether the provisional measures had a binding effect. It reached the following conclusion:

It follows from the object and purpose of the Statute, as well as from the terms of Article 41 when read in their context, that the power to indicate provisional measures entails that such measures should be binding, inasmuch as the power in question is based on the necessity, when the circumstances call for it, to safeguard, and to avoid prejudice to, the rights of the parties as determined by the final judgment of the Court.⁵⁷

The ECtHR has referred extensively to the LaGrand case decided by the ICJ,⁵⁸ in which the mandatory nature of provisional measures was established after decades of doctrinal debates.⁵⁹ It should be noted that in its Cruz Varas case⁶⁰ the ECtHR took a different position as it considered that its procedural rules were not equal to a conventional instrument approved and adopted by states, making it impossible to affirm the binding nature of interim measures in comparison with other systems. Nevertheless, in the Mamatkoulov case the ECtHR emphasised that ‘in the light of the general principles of international law, the law of treaties and international case-law, the interpretation of the scope of interim measures cannot be dissociated from the proceedings to which they relate or the decision on the merits they seek to protect’.⁶¹ The ECtHR stressed the specificity of interim measures within the inter-American system, where the power of the Inter-American Court of Human Rights (IACtHR) to order such measures has an explicit conventional basis.⁶² The ECtHR also recalled, however, that the ICJ in its LaGrand case, the IACtHR, the Human Rights Committee and the Committee against Torture

have confirmed in their reasoning in recent decisions that the preservation of the asserted rights of the parties in the face of the risk of irreparable damage represents an essential objective of interim measures in international law. Indeed, it can be said that, whatever the legal system in question, the proper administration of justice requires that no irreparable action be taken while proceedings are pending.⁶³

Although there was no change to the ECtHR’s procedural rules over the years, nor any amendment to the ECHR, cross-references to the case law of other international bodies allowed the ECtHR to establish the mandatory nature of its provisional measures and to conclude that ‘a failure by a respondent State to comply with interim measures will undermine the effectiveness of the right of individual application guaranteed by Article 34 and the State’s formal undertaking in Article 1 to protect the rights and freedoms set forth in the Convention’.⁶⁴

In their joint partly dissenting opinion, Judges Caflisch, Türmen and Kolver criticised the court’s reasoning. They noted that the ICJ, for instance, was interpreting Article 41 of the ICJ Statute, a provision of a constitutive treaty, whereas the ECtHR was interpreting its procedural rules, to which states have not given their consent.⁶⁵ They stressed that by relying on international instruments and precedents from other international bodies, the ECtHR departed from its own case law and exercised ‘a legislative function, for the Convention as it stands nowhere prescribes that the States Parties to it must recognise the binding force of interim measures indicated’.⁶⁶ As regards crystallisation of the binding nature of provisional measures on the basis of normative convergence in the international legal order, the dissenting judges finally concluded:

There must, however, be a customary rule allowing international courts and tribunals, even in the absence of a treaty provision, to enact Rules of Procedure, a rule which may include the power to formulate interim measures. But that rule cannot be taken to include the power to prescribe such measures.⁶⁷

It is interesting to note that the ECtHR departed from its own precedent, set previously in the Cruz Varas case. It founded its legal reasoning, notably, not on state practice or opinio juris but on the general principles of international law, the law of treaties and international case law,⁶⁸ and on the fact ‘the right of individual application is no longer dependent on a declaration by the Contracting States’.⁶⁹ Even though not affirmed explicitly, the court acknowledged this as a departure from its previous case law, the practice of international courts and tribunals having revealed the binding nature of interim measures to be now part of general international law.

In this example from the ECtHR, cross-references to the case law of other courts were used as a tool to counteract the negative consequences arising from so-called absolute state sovereignty and to bypass normative constraints. The co-ordination and harmonisation of international case law minimises divergent interpretations of a common legal rule such as the binding nature of provisional measures. Interim measures ordered by judicial bodies are aimed at preventing irreversible damage to the rights of parties during executive, legislative and political decision-making processes. As a matter of fact, the binding nature of provisional measures is linked to their function, as the purpose of judicial proceedings is to ensure effective protection of human rights by state authorities required to act in accordance with the rule of law.

Therefore, the growth of multidimensional dialogue between international bodies protecting human rights, between national judges and between international bodies and national judges contributes to the emergence of a network within the international judiciary.⁷⁰ Although operating against the backdrop of distinct and independent legal systems in the international legal order, the international judiciary shares common judicial practices that help to define norms of reference and minimum standards of protection. Nevertheless, these norms and standards need to be incorporated into national legal orders for full applicability and effectiveness, since the primary responsibility to ensure the respect of human rights is devolved to national authorities. Even in the absence of an explicit written rule, international bodies, by applying and interpreting human rights obligations and by sanctioning violations implicating the international responsibility of states, aim to place limits on the exercise of power by framing executive, legislative and political process within the rule of law.

3 Judicial Dialogue as an Approach to Interpretation Leading to Jurisprudential Objectivism and Its Impact on Customary International Human Rights Law

If the will and consent of sovereign states remain at the very foundation of international law and legal systems protecting human rights, the examples previously mentioned and the practice of judicial dialogue show the emergence of jurisprudential objectivism – this arises from a judicial body’s independence and impartiality regarding its nature and functions. Furthermore, jurisprudential objectivism is closely connected to increasing jurisdictionalisation in international law, as demonstrated by the multiplication of international courts and tribunals in diverse fields, especially human rights. Their protection was internationalised with the adoption of the Universal Declaration of Human Rights in 1948, which was the starting point for the internationalisation of human rights protection and has served as a source of inspiration for legally binding treaties. Thus, jurisprudential objectivism embodies a form of autonomy arising from judicial practice that does not depend on states’ interests nor on political or diplomatic views. Moreover, jurisprudential objectivism asserts itself in the face of the will of states when an international court refers spontaneously to decisions or international instruments that are outside its own judicial system, and therefore not included in its constitutive treaty that has been ratified by states parties. The notion of jurisprudential objectivism reflects both the jurisdictionalisation of international obligations and the margin of appreciation exercised by international courts in the interpretation processes. The principles of limited jurisdiction and the required consent to jurisdiction are cornerstones of the very existence of international judicial bodies. The scope of the will and consent of states will be constrained by judicial practice, as the interpretation processes used in case law can lead to objective conclusions, binding on states and detached from the principle of voluntarism.

Jurisprudential dialogue can also be used to identify the emergence of CIL rules determined by other courts, binding on all states, not limited in their application and that do not need express consent – and a fortiori for jus cogens norms that entail erga omnes obligations. In contrast to conventional rules, which can be subject to reservations, ‘this cannot be so in the case of general or customary law rules and obligations which, by their very nature, must have equal force for all members of the international community, and cannot therefore be the subject of any right of unilateral exclusion exercisable at will by any one of them in its own favour’.⁷¹

It is important to emphasise the persuasive authority of the international judiciary and its capacity to build normative convergence through the use of external sources that show an interpretive convergence in the first place. Not only does the practice of judicial dialogue create checks and balances in the international legal order through the comparison of multiple points of view in regard to the interpretation of a specific legal rule; it also enhances the quality of the judgments and their reasoning. When external sources are incorporated in the interpreter’s decision, this improves the legal ruling not only with respect to the requirements of the interpreter’s own system but also in light of the legal requirements that apply in other foreign systems. Consequently, the solution adopted in the court’s decision will be strengthened by a more coherent legal argument, as it has relied on other judicial decisions that reached the same solution when faced with common legal issues.

A stronger legal argument can also enhance the persuasive authority recognised in supranational judgments and decisions that lack the power of enforcement attached to national tribunals and authorities. The legal reasoning and the arguments used in judicial decisions allow the addressees to better understand the extent of their obligations arising from conventional and customary international human rights law. In other words, the practice of referring to multiple sources of law when justifying a legal ruling, whether these sources are judicial decisions or international instruments that show a converging normative content, will enhance the authority of external sources where legal reasoning and justification demonstrate the existence of cross-cutting obligations that do not apply to only one specific legal system but are common to several of them or are part of general CIL.

Indeed, the notion of public international order can be linked to the development of case law of international bodies protecting human rights.⁷² These bodies serve as a last resort to judge human rights violations when the action of national jurisdictions has been insufficient. At the national level, safeguarding public order and security can be used to justify legal restrictions and derogations from the general law in exceptional circumstances. At the international level, the notion of public international order embodies shared values and common principles arising from the necessity to protect human integrity and dignity as cornerstones of the universality of human rights. Public international order also implies the respect of minimum standards and norms of reference, notably through jus cogens norms and erga omnes obligations that are common to legal systems and of interest to the international community as a whole. It is also strongly linked to normative convergence and to jurisprudential objectivism. Normative convergence derived from case law leads to the emergence and the consolidation of jurisprudential objectivism, restraining voluntarism. International obligations that protect core human rights are not based on the will of states but are instead derived from the universality attached to these rights and the protection of the rule of law⁷³ through the respect of minimum standards and norms of reference in light of which human rights violations have to be assessed.⁷⁴ Jurisprudential objectivism results from the practice of international human rights tribunals that leads to strengthening spontaneous international law, beyond binding written agreements, through the identification of cross-cutting customary rules. As judges’ impartiality and independence are central to the scope and function of judicial power, even though political distrust or states’ unwillingness to comply with international obligations may limit their margin of appreciation and lead to negotiated judicial decisions, the binding nature of international customary rules is not altered but rather its effects are being neutralised. Jurisprudential objectivism can also be illustrated by the role played by international courts and tribunals in the determination of customary rules, erga omnes obligations and jus cogens norms that are directly applicable in domestic legal orders, without requiring any legislative implementation or state consent, as they are not defined in conventional instruments but implicitly ensue from them.

Finally, judicial dialogue can be seen as a way to co-ordinate and harmonise the interpretation of key principles of international law, whether written or unwritten, and to acknowledge the international judiciary as a set of mutual interactions and influences between legal systems that strengthen governance in the realm of justice. International bodies, whether judicial or quasi-judicial, and national judges, whether ordinary or constitutional, should engage constantly and on a long-term basis in judicial dialogue, especially when common legal problems are at stake, as is often the case with human rights issues. This implies cooperation and solidarity among those courts and other stakeholders, counteracting the perception that there is a supranational government of judges emerging in the international legal order, in competition with national tribunals and undermining the sovereignty of states.

Nevertheless, there remains the challenge of disseminating the jurisprudential achievements and case law of international bodies in national legal orders, which is the primary responsibility of state authorities. Formal or informal meetings, exchanges and any other kinds of regular interactions and relations that can be developed both between international and national judges could constitute an essential lever to the implementation of a multi-dimensional network spreading information about improvements, challenges and difficulties faced in human rights case law. Undoubtedly, judicial dialogue is a catalyst for strengthening the international judiciary in a globalised world marked by an ever-growing receptivity to external sources. Indeed, just as international bodies refer to one another, they also tend to incorporate references to national tribunals whose case law is relevant to a particular legal matter. National tribunals themselves tend to incorporate domestic norms, international treaties binding on their state, decisions and judgments from national or international jurisdictions and other non-judicial bodies in their interpretation processes. In parallel, many constitutional courts have taken to normative borrowings as a common practice in the process of applying and interpreting national constitutions.⁷⁵ This acknowledgement of their relevance shows an intensification of judicial dialogue at a multi-dimensional level, both horizontal and vertical, but always spontaneous, without any notion of hierarchy, the initiative of engaging in such dialogue and the implications to be drawn being at the discretion of the interpreters participating in such extraterritorial governance.

It is also important to note the role of national judges in defining, applying and taking into account customary international human rights law in domestic court decisions. The protection of human rights is left primarily to national state authorities and judges, with international tribunals intervening only after domestic remedies have been exhausted. Even in states where there is a dualist system of incorporating international law, it has been highlighted that customary international law is immediately applicable without any need of further proceedings or measures,⁷⁶ while ratified treaties require a specific law of implementation to enter into force in the national legal system.⁷⁷ Moreover, customary human rights rules are not only customary but also generally belong to jus cogens and give rise to erga omnes obligations.⁷⁸

4 Concluding Remarks

The practice of judicial dialogue through references to external instruments and the case law of other courts reflects the existence of common standards that transcend the differences and independence between legal systems and emerge as a determining factor in the interpretation and application of rules shared by multiple treaties protecting human rights. Therefore, the eventuality of common standards and norms of references that could be identified in decisions or legal instruments coming under the jurisdiction of other international bodies results in a de facto expansion of possibilities offered to the power of interpretation. Consequently, judicial power attributed to a particular body is strengthened in its relations and interactions with other judicial powers in a mutual process of self-regulation embodied in the practice of judicial dialogue. Indeed, reference to the practice and achievements of other legal systems not only extends the margin of appreciation of the interpreter but also narrows it. Spontaneously, the interpreter will refer to other decisions and instruments that could limit their interpretive possibilities by showing a different state of law, a lack of consensus, or the existence of a strong alternative common interpretation regarding the legal matter at issue. The practice of judicial dialogue belongs within the multiplication of international tribunals and courts linked to the jurisdictionalisation of international human rights law. Far from resulting in a government of judges, it improves extraterritorial governance by a slow but constant movement towards harmonisation through openness to external sources when engaging in interpretation. This practice acquires legitimacy through the sovereign will of states that initially chose to create judicial bodies in the international legal order and to accept their jurisdiction and the margin of appreciation inherent in it.

If mutual inspiration and normative borrowings between international bodies protecting human rights do not always lead to more protective interpretations of human rights, legal precedents could be used as a bulwark against fragmentation by contributing to the realisation of a ‘global community of courts’⁷⁹ through cross-referencing of legal norms and decisions. Indeed, the international legal system can be seen ‘as a collection of communities of practice’,⁸⁰ each area of international law being embodied in a ‘community of practice’ sharing its own conventions, leading principles and rules concerning argumentation and authority. In the field of the protection of human rights, the universal system and the regional systems each represent one ‘community of practice’, co-existing but exercising different jurisdiction and having various functions, while still having a common object and purpose – namely, the protection of human dignity and integrity in accordance with the principle of universality. Indeed, as stated in the ICJ’s famous obiter dictum in the Barcelona Traction case:⁸¹

[A]n essential distinction should be drawn between the obligations of a State towards the international community as a whole, and those arising vis-à-vis another State in the field of diplomatic protection. By their very nature the former are the concern of all States. In view of the importance of the rights involved, all States can be held to have a legal interest in their protection; they are obligations erga omnes.

Such obligations derive, for example, in contemporary international law, from the outlawing of acts of aggression, and of genocide, as also from the principles and rules concerning the basic rights of the human person, including protection from slavery and racial discrimination. Some of the corresponding rights of protection have entered into the body of general international law (Reservations to the Convention on the Prevention and Punishment of the Crime of Genocide, Advisory Opinion, ICJ Reports 1951, p. 23); others are conferred by international instruments of a universal or quasi-universal character.⁸²

Any judicial body interpreting human rights related to its jurisdiction, stands to gain from the global perspective of international law by integrating external sources in its margin of appreciation. Risks and issues arising from the fragmentation of international law were highlighted by Judge Gilbert Guillaume in his address to the General Assembly of the United Nations on 26 October 2000, in which he emphasised that establishing ‘[a] dialogue among judicial bodies is crucial’.⁸³ Fragmentation was also discussed thoroughly in the final report of the study group of the ILC, adopted on 13 April 2006.⁸⁴ Discussions and conclusions emphasised the multiplication of international jurisdictions and positive legal rules in this decentralised order, seen as a threat to the unity and coherence of international law. During recent years, however, the development of judicial dialogue between international bodies protecting human rights has shown that in spite of their independence and the absence of a hierarchical principle of organisation, the power of interpretation that might lead to divergent jurisprudential achievements tends to self-regulate. Even though external references are not included systematically in all decisions and judgments of international courts and tribunals, they tend to be mentioned in important judgments and decisions, notably when common legal issues of great importance are at stake or when cross-cutting rules appear to be part of CIL. Spontaneous normative borrowings seem to extend the margin of appreciation and interpretative authority of any international court, for, in referring to instruments and decisions that are not initially part of its system, it goes beyond the limits set by the instrument defining its jurisdiction, functions and powers. However, the taking account of similar case law when ruling on analogous legal issues in human rights matters opens the way to common solutions reflecting normative convergence. This all contributes to the process of harmonisation in the application and interpretation of human rights instruments and identification of rules that have become part of customary international law. Moreover, because judicial dialogue is not a binding obligation, a particular body’s openness to external sources illustrates a search for and willingness to embrace the implicit perspective of universal justice in reflection of the universality characterising fundamental human rights notwithstanding differences of culture, tradition and legal practice.⁸⁵