I. Introduction
The right of self-defence is conferred on States by treaty and customary international law.Footnote 1 At the same time, treaty and customary law impose a number of restrictions on the exercise of this right: self-defence is limited to those circumstances in which an ‘armed attack’ occurs;Footnote 2 defensive action must not go beyond what is necessary and proportionate to repel an armed attack;Footnote 3 instances of self-defence must be reported to the Security Council (SC) of the United Nations (UN);Footnote 4 and the right of self-defence is suspended as soon as the SC adopts measures necessary to maintain international peace and security.Footnote 5 Ordinarily, States rely on the right of self-defence to justify measures that would otherwise contravene the prohibition on the threat or use of force under Article 2(4) UN Charter and customary law.Footnote 6 In this context, measures are forcible where they involve the threat or use of ‘violence’;Footnote 7 that is, where they cause (or threaten to cause) ‘destruction to life and property’.Footnote 8 Given that States usually invoke the right of self-defence to justify forcible responses to armed attacks, the prevailing view among international lawyers is that this right is subject to an additional restriction; namely, that it can be engaged only when States threaten or use force to resist an armed attack.Footnote 9 In this way, the right of self-defence is presented as an exception to the principle of non-use of force.
This conception of the right of self-defence is problematic because States may respond to armed attacks with non-forcible measures. For example, and as discussed in detail below, during the 1982 Falklands War certain States imposed economic sanctions against Argentina and justified them as acts of collective self-defence on the basis that they were designed to halt and repel Argentina's armed attack against the United Kingdom (UK). In 2002, Israel built a security wall within occupied Palestinian territory and justified it as an act of self-defence, claiming the wall was necessary to protect its population from armed attacks that were being launched by pro-Palestinian groups. More recently, States have indicated their willingness to launch cyber operations under the banner of self-defence in order to counter armed attacks.
Economic sanctions, security barriers and cyber operations are unlikely to rise to the level of a use of force given that they do not usually cause death, injury, destruction or damage to people or property. Yet importantly, they may run into conflict with other rules of international law such as the principles of territorial sovereignty and non-intervention or, with regard to economic sanctions, they may breach international trade, economic or investment law. If States have an ‘inherent right’ to defend themselves against armed attacks as Article 51 UN Charter explains, the question arises as to how such non-forcible measures can be justified under international law. As this article reveals, many international lawyers take the position that non-forcible responses to armed attacks should be classified as countermeasures. But this classification is inappropriate given that the doctrine of countermeasures is a law enforcement mechanism and, as such, it is subject to a range of conditions and restrictions that would prevent States from defending themselves effectively against armed attacks.
The core claim of this article is that self-defence is a general right under international law and can be invoked to justify all measures necessary to repulse an armed attack regardless of whether they are forcible or non-forcible in nature. In practical terms, reconceptualising self-defence as a general right is important for two main reasons. First, it enhances the effectiveness of the right of self-defence by broadening the response options available to victim States—in short, it enables them to confront armed attacks with a range of non-forcible and forcible measures. Secondly, it can help prevent the unnecessary escalation of crises by allowing victim States to respond to armed attacks with non-forcible measures. By contrast, construing self-defence as an exception to the principle of non-use of force would require victim States to use force to resist armed attacks, which runs the risk of unnecessarily aggravating crises if non-forcible measures would be sufficient to counter them.
In making the claim that self-defence is a general right under international law, this article adheres to the following structure. To set the scene, Section II reveals that the conventional wisdom among international lawyers is that the right of self-defence is only available where States respond to armed attacks with force. Rejecting this mainstream account, Section III presents the doctrinal evidence to support the argument that the right of self-defence also permits States to use non-forcible measures to fight off an armed attack. This evidence includes an examination of the genesis of the right of self-defence under customary law, the text of Article 51 UN Charter, the structure of the UN Charter and State practice on Article 51. Section IV focuses on countermeasures since, according to many international lawyers, non-forcible responses to armed attacks should be accommodated within this doctrine. While the doctrines of countermeasures and self-defence may overlap insofar as they can apply to the same set of circumstances, Section IV demonstrates that there are nevertheless compelling conceptual, theoretical and doctrinal reasons why the use of non-forcible measures to repel an armed attack should be characterised as an act of self-defence rather than a countermeasure. Section V provides conclusions.
II. Conventional Wisdom: Self-Defence as Counter-Force
As has been seen, in 2002 Israel built a security wall within occupied Palestinian territory to protect its population from terrorist attacks.Footnote 10 While members of the international community alleged that the construction of the wall breached international human rights law and international humanitarian law,Footnote 11 Israel justified it as an act of self-defence under Article 51 UN Charter.Footnote 12
In December 2003, the UN General Assembly (GA) requested an Advisory Opinion from the International Court of Justice (ICJ) on the legal consequences arising from Israel's construction of the wall.Footnote 13 In its Advisory Opinion to the GA, the ICJ found that the construction and permanence of the wall breached international human rights law and international humanitarian law.Footnote 14 Moreover, the Court rejected Israel's claim of self-defence on the grounds that, first, this right cannot be engaged against a non-State actor and, second, the author of the armed attack cannot be located within the victim's State's territory or territory under its occupation.Footnote 15 Having dismissed Israel's claim to self-defence on these bases, the Court did not have to examine whether this right can be invoked to justify the use of non-forcible measures such as the building of a security wall. However, in her Separate Opinion Judge Higgins turned her attention to this question and, in a brief but important passage, she explained:
I remain unconvinced that non-forcible measures (such as the building of a wall) fall within self-defence under Article 51 of the Charter as that provision is normally understood.Footnote 16
It is notable that Judge Higgins did not provide any legal justification or cite any authority to substantiate her statement. This notwithstanding, her argument is shared by numerous international lawyers.
Special Rapporteurs for the International Law Commission's (ILC) project on the law of State responsibility construed the right of self-defence as an exception to the principle of non-use of force, even if they held different views on how these provisions interact. For Roberto Ago (the project's second Special Rapporteur), the right of self-defence operates as a secondary rule of international law insofar as it precludes State responsibility for breaches of the non-use of force principle.Footnote 17 By contrast, James Crawford (the project's final Special Rapporteur) regarded self-defence as being so closely related to the prohibition on the threat or use of force that he saw it as forming an integral part of the prohibition itself.Footnote 18 Crawford therefore argued that Articles 2(4) and 51 UN Charter must be read together as a singular primary rule of international law: States cannot threaten or use force in their international relations except in self-defence. According to this approach, ‘[a] State exercising its inherent right of self-defence as referred to in Article 51 of the Charter is not, even potentially, in breach of Article 2, paragraph 4’.Footnote 19
Importantly, Crawford's view that self-defence under Article 51 UN Charter is an exceptional right intrinsic to the non-use of force principle was adopted by the ILC in its Commentary to Article 21 of the Articles on State Responsibility (ASR),Footnote 20 which explains:
Article 51 of the Charter of the United Nations preserves a State's “inherent right” of self-defence in the face of an armed attack and forms part of the definition of the obligation to refrain from the threat or use of force laid down in Art 2, paragraph 4.Footnote 21
Article 21 ASR also governs the matter of self-defence but must not be confused with Article 51 UN Charter. Article 21 ASR is a secondary rule of international law and precludes State responsibility for ancillary or incidental violations of international law that occur as a result of defensive measures being taken under Article 51 UN Charter, such as breaches of the principles of territorial sovereignty and non-intervention, a treaty of amity, a trade treaty, etc. As the Commentary to Article 21 ASR explains, ‘[s]elf-defence [under Article 21 ASR] may justify non-performance of certain obligations other than that under Article 2, paragraph 4, of the Charter of the United Nations, provided that such non-performance is related to the breach of that provision’.Footnote 22 As this quotation makes clear, Article 21 ASR cannot be relied upon independently of Article 51 UN Charter to justify the use of non-forcible defensive measures.Footnote 23
The claim that self-defence (as a primary rule) can only be relied on to justify forcible responses to armed attacks is also widely supported in the academic literature.Footnote 24 Expressly defending Judge Higgins's conclusion that the right of self-defence does not cover non-forcible measures, Scobbie explains that it:
is clearly supported by both the development of the prohibition on the use of force in international relations and by the logic of the UN Charter. Self-defence is universally regarded as one of the two exceptions to the prohibition on the use of force provided by the UN Charter … Any measure short of force cannot therefore be classified as amounting to self-defence undertaken in pursuit of Article 51 of the UN Charter.Footnote 25
As already indicated, the central thesis of this article is that the right of self-defence permits the use of forcible and non-forcible measures to fend off an armed attack. While a small number of commentators have made this argument, they do so en passant and, because their focus is on other aspects of the right of self-defence, they do not advance any theoretical or doctrinal justification to support their claim.Footnote 26
III. Self-Defence and Non-Forcible Measures
This section demonstrates that, as a matter of lex lata, the right of self-defence can be relied on to justify all measures necessary to ward off an armed attack. This argument is made through an examination of the origins of the right of self-defence under customary law, the text of Article 51 UN Charter, the structure of the UN Charter and State practice on Article 51.
A. The Origin of Self-Defence: The Duty of Self-Preservation
Article 51 UN Charter describes self-defence as an ‘inherent right’ and, as the ICJ has explained, this phrase refers to the ‘pre-existing customary international law’ basis of this doctrine.Footnote 27 As nothing within Article 51 ‘shall impair’ the inherent right of self-defence, the objective of this provision is to preserve the customary right of self-defence and carry it forward into the Charter era, albeit subject to certain modifications. Thus, an inquiry into the customary practice of the right of self-defence prior to the adoption of the UN Charter is essential if one is to understand the content of this right under contemporary international law.
Historically, the right of self-defence was part of the duty of self-preservation.Footnote 28 Self-preservation was a natural law duty that required States to take all measures necessary to preserve their essential interests: ‘the so called right of self-preservation was … the virtually unrestricted freedom it gives to a state to act contrary to any norm of International Law, if such action is deemed necessary for its own preservation’.Footnote 29
States refined the duty of self-preservation during the nineteenth century. What emerged was a right of self-defence and, being a product of State practice and opinio juris, it was a legal right conferred by way of customary law.Footnote 30 Over time, States developed customary law and placed limits on when and how the right of self-defence could be exercised—for example, by the mid-nineteenth century it was accepted that defensive action could not go beyond what was necessary and proportionate to avert the threat of harm.Footnote 31 Importantly, States did not restrict the right of self-defence to the use of forcible measures exclusively. As a review of State practice reveals, in pursuit of self-defence States were free to take all measures necessary to protect themselves from harm irrespective of which rules of international law they breached.
During the nineteenth century, the United States (US) regularly conducted military operations in Mexico to prevent Native Americans conducting attacks within US territory. In July 1836, suspecting that Native Americans in Texas (then part of Mexico) were planning raids within the US, the US sent troops into Mexico and occupied parts of its territory and justified this action on the basis of ‘the immutable principle of self-defense’.Footnote 32 Mexico's Minister to the US concluded that the US's invocation of self-defence was not warranted in the circumstances and determined that ‘[t]he honour and rights of my Country are … greatly compromised by the violation of its territory and subsequent occupation’ by US forces.Footnote 33 In response, the US explained:
The present inability of Mexico to restrain the Indians within her territory from hostile incursions upon the citizens of the United States, if they should once be engaged in hostility near the frontier, and the barbarous character of their warfare which respects neither the rights of nations nor of humanity, renders it imperative on the United States to adopt other means for the protection of their citizens. What those means should be, must depend upon the nature of the danger. Should that require the temporary occupation of posts beyond the frontier, the duty of self-preservation gives them the right to such occupation.Footnote 34
As this correspondence reveals, neither the US nor Mexico discussed the right of self-defence in the context of the use of military force. Instead, the question was whether self-defence could be relied on to justify a State's non-consensual intrusion into another State's territory, that is, whether self-defence could be invoked to justify a violation of the principle of territorial sovereignty. By answering this question in the positive, both States accepted that—as a matter of legal principle—self-defence was a general right under international law and could be invoked to justify the use of all measures necessary to avert the threat of harm.
In December 1837, British forces entered US territory to destroy the Caroline, a steamer being used to ferry weapons and other supplies to rebel groups in Upper Canada who were revolting against British rule. British forces killed at least one American national and, subsequently, fired the steamer and set it sail over Niagara Falls. This incident precipitated a significant diplomatic fallout between the UK and US which, over several years, exchanged correspondence debating the legality of the former's actions.
Usually, the Caroline incident is discussed in relation to whether the right of self-defence can be engaged to neutralise threats of anticipated harm or to confront threats posed by non-State actors. What is often overlooked is that the right of self-defence was discussed in the context of the UK's violation of the US's territorial sovereignty generally rather than the UK's use of force against the US specifically.Footnote 35 For example, the US Minister in London protested against the UK's actions and claimed that international law prohibits non-consensual ‘entry into the territory of an independent state’, although he recognised that such entry is permitted ‘in cases of extreme state necessity’.Footnote 36 Similarly, the US Secretary of State explained:
The President sees with pleasure that your Lordship fully admits those great principles of public law, applicable to cases of this kind, which this Government has expressed; and that on your part, as on ours, respect for the inviolable character of the territory of independent states is the most essential foundation of civilization. And while it is admitted on both sides that there are exceptions to this rule, he is gratified to find that your Lordship admits that such exceptions must come within the limitations stated and the terms used in a former communication from this Department to the British Plenipotentiary here. Undoubtedly it is just, that while it is admitted that exceptions growing out of the great law of self-defence do exist, those exceptions should be confined to cases in which the “necessity of that self-defence is instant, overwhelming, and leaving no choice of means, and no moment for deliberation”.Footnote 37
Responding to the US Secretary, the British Special Minister agreed that respect for territorial inviolability was a foundational principle of international law and that, exceptionally, trespass into another State's sovereign territory was permitted where necessary to achieve self-defence.Footnote 38
In 1867, the US extended its jurisdiction over the Bering Sea after it purchased Alaska from Russia. The US alleged that Canadian vessels were hunting seals that were migrating through the Bering Sea, which it saw as unlawfully interfering with the commercial rights of US companies as guaranteed by US law. In 1886, US authorities apprehended a number of Canadian vessels while they were hunting for seals. As Canada was under British rule at the time, it was the UK who protested against the seizure of the vessels. After diplomatic efforts to resolve the dispute ended unsuccessfully, the UK and US signed a treaty of arbitration and a Tribunal was established to consider a number of issues, one of which was: ‘Has the United States any right, and if so, what right of protection or property in the fur seals frequenting the islands of the United States in Bering Sea when such seals are found outside the ordinary three-mile limit [that falls with a State's territorial sea]’.Footnote 39
During the proceedings, the US asserted its right of self-defence to seize the Canadian vessels on the basis that such action was necessary to protect its essential interests:
[T]he right of self-defense on the part of a nation is a perfect and paramount right to which all others are subordinate, and which upon no admitted theory of international law has ever been surrendered; that it extends to all the material interests of a nation important to be defended; that in the time, the place, the manner, and the extent of its execution it is limited only by the actual necessity of the particular case … and that whenever an important and just national interest of any description is put in peril for the sake of individual profit by an act upon the high sea, even though such act would be otherwise justifiable, the right of the individual must give way, and the nation will be entitled to protect itself against the injury by whatever force may be reasonably necessary, according to the usages established in analogous cases.Footnote 40
As can be seen, the US saw self-defence as a right ‘to which all others are subordinate’ and, in this particular instance, could be invoked to justify an interference with the principle of the freedom of the high seas. Ultimately, the Tribunal did not have to address the doctrine of self-defence, instead finding the US liable for its apprehension of the Canadian vessels on the basis that its territorial sea did not extend to the waters in which the vessels were seized and thus it did not have a right to protect seals in that area.Footnote 41
The use of force is of course bound up with these instances of State practice insofar as the US's incursion into Mexico and the UK's intervention in the US involved military personnel crossing the borders of other States and using force and, in the Bering Sea incident, the US Coast Guard boarded Canadian fishing vessels and apprehended their crews. The reason why these States engaged the right of self-defence to justify breaches of the principles of territorial sovereignty and the freedom of the high seas rather than the non-use of force was because, in the nineteenth century, there was no specific prohibition on the use of force (or even war) under international law. As Brownlie demonstrates, the prohibition on the use of force crystallised as a rule of customary law at some point between 1928 and 1945.Footnote 42 Thus, during the nineteenth century the legality of military interventions within States was assessed according to other rules of international law, such as the principles of territorial sovereignty and non-intervention. What this shows is that the right of self-defence predates the principle of non-use of force and that, critically, these provisions developed at different points in time and in different contexts.
As the above case studies illustrate, during the nineteenth century the right of self-defence was seen as a general right under customary law that could be asserted to justify any conduct irrespective of which rule of international law it breached, provided of course the defensive action was necessary to protect the essential interests of the State. The principle of non-use of force was grafted onto international law via customary and treaty law at a later date and, as will be seen below, in the years that followed States did not reformulate the right of self-defence as an exception to the principle of non-use of force—rather, States maintained the position that self-defence is a general right under international law.
B. Text of Article 51 UN Charter
The UN Charter was adopted in 1945 and, as explained previously, Article 51 preserves the right of self-defence under customary law. At the same time, Article 51 integrates the right of self-defence into the collective security system and makes it suitable for the Charter era. To do so, Article 51 subjects the customary right of self-defence to a number of restrictions. For example, to enable the collective security system to function effectively, Article 51 requires States to report their invocations of the right of self-defence to the SC and suspends this right where the SC adopts measures necessary to restore international peace and security. The question that arises is whether Article 51 places limits on the types of measures a victim State can undertake in the name of self-defence; namely, whether Article 51 restricts the right of self-defence to the threat or use of force.
Article 51 explains that ‘[n]othing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs’. As is apparent, the text of Article 51 does not limit the customary right of self-defence to forcible measures. As Tams observes:
There is little indication in Art. 51 that measures of self-defence has [sic] to involve the use of force; where the defending state seeks to defend itself by measures not involving recourse to force (e.g., blockades), these will a fortiori be justified.Footnote 43
This reading of Article 51 UN Charter is supported by the interpretative maxim in eo quod plus sit semper inest et minus (‘in the greater is always included the lesser’),Footnote 44 which is designed to give effect to the ordinary meaning of treaty provisions.Footnote 45 This maxim is often used to determine the scope of rights and powers granted by treaties. For example, in the Application for Review case Judge de Castro relied on this maxim to conclude that, because the UN Charter confers on the GA the power to request advisory opinions and authorises other organs and specialised agencies to do so, and grants the GA the power to establish subsidiary organs, the GA must have the power to bestow on these organs the right to seek advisory opinions.Footnote 46 If the ‘greater includes the lesser’, as this maxim prescribes, the right to use force in self-defence must include the right to use non-forcible measures in self-defence.Footnote 47 In fact, Israel's representative to the UN appeared to invoke the maxim in eo quod plus sit semper inest et minus when concluding that, as a matter of interpretative logic, Article 51 must permit the use of non-forcible and forcible measures:
International law and Security Council resolutions, including resolutions 1368 (2001) and 1373 (2001), have clearly recognized the right of States to use force in self-defence against terrorist attacks, and therefore surely recognize the right to use non-forcible measures to that end.Footnote 48
C. Structure of the UN Charter
The structure of a treaty can be used to interpret the meaning of its provisions.Footnote 49 Importantly, the principle of non-use of force under Article 2(4) UN Charter appears in Chapter 1 of the Charter, which enumerates the UN's purposes and principles. By contrast, the right of self-defence is contained in Article 51 and this provision is located within Chapter VII of the Charter, which regulates the UN's collective security system. If self-defence can be engaged only in the context of forcible responses to armed attacks—that is, Article 51 is a built-in exception to Article 2(4)—it must be questioned why these provisions appear in different chapters of the Charter and why they are not connected in any structural manner. Rather than being an exception to Article 2(4), the structure of the Charter indicates that Article 51 is an exception to the UN's collective security system.
To explain, while the SC has primary responsibility for the maintenance of international peace and security, where an armed attack occurs States have a right under Article 51 to engage in defensive action independent of SC approval and this right persists up to the moment that the Council adopts measures necessary to restore international peace and security. Importantly, the travaux préparatoires reveal that the drafters of the UN Charter saw Article 51 as constituting an exception to the collective security system rather than Article 2(4).Footnote 50 For example, commenting on a draft of Article 51 the Chinese delegate to the San Francisco conference explained that ‘this article amounts to an exception to the enforcement arrangements decided upon by the Security Council’.Footnote 51
D. State Practice on Article 51 UN Charter
Under Article 31(3)(b) of the Vienna Convention on the Law of Treaties 1969, State practice subsequent to a treaty coming into force can be used to interpret that treaty where it establishes the agreement of the parties. Since the inception of the UN Charter, State practice on Article 51 confirms that the doctrine of self-defence encompasses the right to deploy non-forcible and forcible measures to counter an armed attack.Footnote 52
1. Regional security arrangements
The Inter-American Treaty of Reciprocal Assistance (otherwise known as the Rio Treaty) was signed in 1947 and Article 3(1) establishes a collective self-defence pact:
The High Contracting Parties agree that an armed attack by any State against a State Party shall be considered an attack against all the States Parties and, consequently, each of them undertakes to assist in meeting any such attack in the exercise of the inherent right of individual or collective self-defense recognized by Article 51 of the Charter of the United Nations.
Where members come to the assistance of an attacked member, Article 3(2) provides:
[E]ach of the States Parties may determine, according to the circumstances, the immediate measures it may take individually in fulfillment of the obligation set forth in the preceding paragraph.
Finally, Article 3(6) explains:
Measures of self-defense provided for under this Article may be taken until the Security Council of the United Nations has taken the measures necessary to maintain international peace and security.
As can be seen, Articles 3(2) and (6) refer to ‘measures’ taken in exercise of the right of self-defence, indicating that defensive action can involve measures generally rather than the use of force specifically. Importantly, Article 3(1) explicitly states that its articulation of the right of self-defence is consistent with this right as it is enshrined in Article 51 UN Charter. Indeed, the right of individual and collective self-defence was expressly included in the UN Charter at the behest of Latin American States who were keen to preserve the Act of Chapultepec, which was a regional mutual assistance arrangement adopted two months before the signing of the UN Charter and was later formalised by the Rio Treaty.Footnote 53 Accordingly, it can be said that members of the Rio Treaty perceive Article 51 UN Charter as affording victim States the right to use all measures necessary to combat an armed attack.
In 1949, the North Atlantic Treaty was signed and the North Atlantic Treaty Organization (NATO) was thereby established. Like the Rio Treaty, the North Atlantic Treaty establishes a collective self-defence pact and Article 5 provides:
The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
The language employed by the North Atlantic Treaty is even clearer than the Rio Treaty. Article 5 requires a member to come to the assistance of an attacked member and, when requested, permits it to take ‘such action as it deems necessary, including the use of armed force’. The critical word here is ‘including’, which indicates that members can render assistance to a fellow member including but not limited to the use of armed force.
During the drafting of the North Atlantic Treaty the US Senate expressed concern over an earlier draft of Article 5 that would have required member States to provide military assistance to fellow members in the event that they fell victim to an armed attack.Footnote 54 At the same time, the US remained committed to the overarching objective of NATO, which was to create a collective self-defence pact where members are required to come to the assistance of other members when they are attacked. By way of compromise, the US advocated for a formulation of Article 5 that retained the mutual assistance obligation but which allowed members to decide for themselves what type of support they would render to an attacked member and, in particular, whether they would provide military or non-military assistance. The product was Article 5, which allows a NATO member to provide the assistance ‘it deems necessary, including the use of armed force’.
That Article 5 covers the use of non-forcible measures is also supported by the practice of NATO and its member States. After the 9/11 terrorist attacks against the US, NATO determined that an armed attack had been committed against a member State and, for the first time in its history, engaged Article 5 of the North Atlantic Treaty. Pursuant to Article 5, NATO agreed a number of measures to support the US:
• Enhance intelligence sharing and cooperation between NATO members;
• Increase security for US facilities on the territory of NATO members;
• Provide blanket overflight clearances for US military aircraft related to operations against terrorism;
• Provide the US with access to ports and airfields on the territory of NATO members for operations against terrorism; and
• Affirmed its readiness to deploy NATO's Standing Naval Force and Airborne Early Warning Force to support US operations against terrorism.Footnote 55
Evidently, the measures agreed under Article 5 include non-forcible measures. Some of these measures were put into practice in October 2001 when NATO launched operation Active Endeavour, which involved its Standing Naval Force patrolling the eastern Mediterranean and monitoring shipping in order to detect and deter terrorist activity, including illegal trafficking. This operation was expanded in March 2004 to include the entire Mediterranean.Footnote 56
Importantly, as with the Rio Treaty, Article 5 of the North Atlantic Treaty expressly situates its discussion of the right of self-defence within the framework of Article 51 UN Charter, indicating that NATO members regard the definition of collective self-defence under Article 5 of the North Atlantic Treaty as mirroring the definition of this right under Article 51 UN Charter.Footnote 57 Moreover, Article 7 of the North Atlantic Treaty explicitly declares that nothing in the agreement affects the rights and obligations arising under the UN Charter.Footnote 58 That the right of self-defence as outlined in Article 5 of the North Atlantic Treaty is consistent with the right of self-defence as set out in Article 51 UN Charter is further indicated by the drafting history of the North Atlantic Treaty. For example, States such as the US made it clear that their accession to NATO was on the understanding that the terms of the North Atlantic Treaty were compatible with the ‘purposes, principles, and provisions of the [UN] Charter’.Footnote 59
In 1950, Egypt, Iraq, Jordan, Lebanon, Saudi Arabia, Syria and Yemen signed the Treaty of Joint Defense and Economic Cooperation. Article 2 of this agreement affirms the right of individual and collective self-defence where a member falls victim to armed aggression. More specifically, Article 2 recognises that the right of self-defence permits States ‘to take, individually or collectively, all steps available, including the use of armed force, to repel the aggression and restore security and peace’. As with the North Atlantic Treaty, the language of this provision is significant. By permitting States to take ‘all steps available’ to confront acts of armed aggression ‘including’ the use of armed force, Article 2 makes it clear that the right of self-defence covers the use of non-forcible and forcible measures. Article 2 also explains that the parties to this agreement must act ‘[i]n conformity’ with Article 51 UN Charter by, for example, notifying the SC when they invoke the right of self-defence. This reference to Article 51 UN Charter indicates that the members of the Treaty of Joint Defense and Economic Cooperation see this agreement's articulation of the right of self-defence as aligning with the definition of the right of self-defence under Article 51 UN Charter. If this is the case, it is reasonable to assume that the members of this treaty see Article 51 UN Charter as permitting the use of all measures necessary to counteract an armed attack.
2. Economic sanctions: the Falklands War
On 2 April 1982 Argentina invaded the Falkland Islands, which is territory under British sovereignty. The following day the SC adopted Resolution 502 (1982), declaring that the situation constituted a ‘breach of the peace’, condemning Argentina's ‘invasion’ and demanding the ‘immediate withdrawal’ of Argentinian forces. That said, the SC did not authorise enforcement action against Argentina.
The UK invoked Article 51 UN Charter and commenced military action against Argentina. At the request of the UK,Footnote 60 on 10 April 1982 ten European States imposed a temporary general import embargo on Argentinian goods.Footnote 61 Days later, the European Economic Community (EEC) imposed a comprehensive embargo on goods being imported from Argentina,Footnote 62 as did Australia,Footnote 63 CanadaFootnote 64 and New Zealand.Footnote 65 Argentina subsequently lodged a complaint before the GATT Council of Representatives, arguing that the embargoes breached the General Agreement on Tariffs and Trade (GATT) 1947.Footnote 66 In response, Australia, Canada and the EEC issued a joint communiqué conceding that their embargoes ran into prima facie conflictFootnote 67 with Argentina's rights under the GATT but justified any infraction on the basis of ‘their inherent rights of which Article XXI of the General Agreement is a reflection’.Footnote 68
Article XXI GATT permits States to derogate from this agreement where necessary to protect their ‘essential security interests … in time of war or other emergency in international relations’. However, two factors militate against the conclusion that the embargoes were deployed pursuant to this treaty-specific provision. First, the communiqué's assertion that the legal basis of the embargoes was a ‘reflection’ of Article XXI indicates that the source of their legal authority was located in general international law and which had been codified in the GATT.Footnote 69 As the EEC representative explained during the debates, ‘[t]he exercise of these rights constituted a general exception to the GATT’.Footnote 70 Second, as well as violating the GATT, the EEC's embargo breached obligations it owed to Argentina under two sectoral agreements on trade in textiles and trade in lamb and mutton.Footnote 71 Evidently, the EEC could not invoke the national security exception contained in Article XXI GATT to justify its breach of these agreements, which means their legal basis must have resided elsewhere.
It has been argued that the embargoes against Argentina were deployed as collective countermeasures in support of the UK.Footnote 72 The doctrine of countermeasures is discussed in detail below and, as will be seen, injured States can take countermeasures against wrongdoing States. Some international lawyers go further and argue that States can take countermeasures against wrongdoing States where there has been a breach of an obligation owed to the international community as a whole (obligations erga omnes), a doctrine known as collective countermeasures.Footnote 73 If this argument is correct, it may be the case that Argentina's armed attack against the UK constituted an act of aggression and, given that the prohibition on aggression is typically regarded as an erga omnes obligation,Footnote 74 this conduct permitted States to engage in collective countermeasures against Argentina.
Whether collective countermeasures are permissible under international law is very much contested. While the ILC found that State practice in favour of collective countermeasures is too ‘sparse’ and ‘limited’ to conclude that the doctrine of collective countermeasures is established in customary law,Footnote 75 commentators have claimed that this practice is thicker than the ILC realised and, consequently, collective countermeasures are lawful.Footnote 76 But even if it is assumed arguendo that States can take collective countermeasures in order to protect collective legal interests, it is important to highlight that the joint communiqué justified the embargoes on the basis of ‘inherent rights’.Footnote 77 Similarly, New Zealand explained that it ‘had an inherent right to take such action as a sovereign State’.Footnote 78 This language seems to exclude the possibility that countermeasures constituted the legal basis of the embargoes because, as shall be seen below, countermeasures operate as excuses rather than justifications and, as such, it is inaccurate to refer to them as the exercise of an inherent right. Self-defence, however, is unmistakably known as an inherent right and, in fact, this is how Article 51 UN Charter refers to it. The language of ‘inherent right’ therefore points to the conclusion that these actors justified their embargoes against Argentina on the basis of the collective self-defence of the UK.Footnote 79 Importantly, Canada seemed to justify its embargo as an act of collective self-defence. According to the Canadian Secretary of State for External Affairs:
What is of great concern to Canada and to other peace abiding countries is that Argentina has chosen to try to settle a dispute over territory by recourse to force of arms and that the United Kingdom has had to have recourse to self-defence in order to regain those islands. That is the position that Canada has taken. It is in pursuance of that position that we have banned the export of war material to Argentina and that we have, like the members of the Common Market, imposed similar kinds of restrictions with respect to the entry of Argentinian imports to Canada.Footnote 80
Furthermore, when the ten European States deployed embargoes against Argentina on 10 April 1982, they informed the SC that they were engaging in this action.Footnote 81 This is important because Article 51 UN Charter requires that ‘measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council’. Admittedly, the report of the ten European States did not expressly identify the right of self-defence as the legal basis of the embargoes. However, Article 51 does not prescribe what format a report should take or what its contents should beFootnote 82—instead, all Article 51 requires is that States make the SC aware of the measures they have taken pursuant to the right of self-defence, and in doing so they can expressly identify self-defence as the legal justification for their measures or this can be inferred from the context of the notification. Thus, the fact that the ten European States saw it as necessary to report their deployment of the embargoes to the SC, coupled with the report's determination that this action was justified on the basis ‘of the invasion of the Falkland Islands by Argentina’,Footnote 83 indicates that these measures were imposed pursuant to the right of collective self-defence. By contrast, States do not have to notify the SC when they resort to countermeasures.
3. Security wall: Israel
As has been seen above, in 2002 Israel sought to protect its population from armed attacks by constructing a security wall within occupied Palestinian territory. Israel did not regard its construction of the wall as involving a use of force within the meaning of Article 2(4) UN Charter.Footnote 84 Rather, Israel characterised the wall as a non-forcible measure and expressly justified it as an act of self-defence under Article 51 UN Charter. Before the GA, Israel's representative to the UN explained that:
[A] security fence has proven itself to be one of the most effective non-violent methods for preventing terrorism in the heart of civilian areas. The fence is a measure wholly consistent with the right of States to self-defence enshrined in Article 51 of the Charter.Footnote 85
Israel was therefore unambiguous in its contention that the right of self-defence can be relied on to justify the use of non-forcible measures. Interestingly, while members of the GA were highly critical of Israel's decision to build a wall, no State within the GA criticised (let alone rejected) Israel's determination that the right of self-defence extends to the use of non-forcible measures, which seems to indicate their acceptance of this interpretation of the doctrine of self-defence.
4. Cyber operations: USA
International law applies to cyberspace and the activities occurring within it.Footnote 86 While States agree that cyber operations can breach the principle of non-use of force, they disagree as to the threshold at which this occurs. For example, some States maintain that it is only those cyber operations producing offline, physical damage that constitute a use of force, while others hold that cyber operations causing online harm can qualify as a use of force where they seriously impact upon the functionality of a computer system or network.Footnote 87 Conceivably, a State may attempt to fight off an armed attack by launching a cyber operation that does not rise to the level of a use of force, but which nevertheless breaches other rules of international law such as the principles of territorial sovereignty and non-intervention.
Consider, for instance, a situation in which a State seeks to counter an armed attack by launching a cyber operation that temporarily disrupts the attacking State's military communications systems. Most commentators agree that this type of cyber operation constitutes a prima facie breach of the principle of territorial sovereignty or even the principle of non-intervention but, given that it only causes temporary disruption to the computer systems of the attacking State, it does not qualify as a breach of the non-use of force principle.Footnote 88 Given that the victim State is responding to an armed attack, the question arises as to how these types of defensive, non-forcible, prima facie unlawful cyber operations are to be appraised under international law.
The US Department of Defense (DoD) has adopted a strategy of ‘defend forward’ when it comes to confronting adversaries in cyberspace. According to the DoD, ‘defend forward’ means to ‘disrupt or halt malicious cyber activities at its source, including activity that falls below the level of armed conflict’, and it often includes extraterritorial operations.Footnote 89 The DoD further explains that this strategy ‘seeks to pre-empt, defeat, or deter malicious cyber activity targeting U.S. critical infrastructure that could cause a significant cyber incident … Our primary role in this homeland defense mission is to ‘‘defend forward’’ by leveraging our focus outward to stop threats before they reach their targets.’Footnote 90
The DoD's ‘defend forward’ strategy covers non-forcible and forcible cyber operations, but it does not explain what their legal basis is when they run into conflict with international law. Where the US falls victim to a breach of international law and engages in non-forcible cyber operations that are prima facie unlawful, they can qualify as countermeasures if they meet the conditions of this doctrine. Importantly, however, where these non-forcible cyber operations are in response to an armed attack, the DoD's language indicates that they can be justified as acts of self-defence because, after all, the strategy is called ‘defend forward’ and its aim is to ‘stop threats’ and protect ‘targets’.Footnote 91 As such, the DoD's strategy implies that the US regards the right of self-defence as extending to non-forcible as well as forcible measures.
IV. Distinguishing the Doctrines of Countermeasures and Self-Defence
Most commentators claim that, where a State suffers an armed attack and responds with non-forcible measures that are prima facie unlawful, it must rely on the doctrine of countermeasures to shield itself from international legal responsibility. For example, Sicilianos rejects Bowett's claimFootnote 92 that States can invoke the right of self-defence to justify the use of non-forcible measures such as economic sanctions:
[Ceci] ne signifie aucunement toutefois que l'Etat victime d'une agression armée (ou ses alliés) ne pourraient réagir cumulativement par la force et par des mesures économiques ou autres. Ces derniéres, si elles sont en soi illicites, seront justifiées au titre de contre-mesures.Footnote 93
Under general international law, countermeasures are otherwise unlawful acts that are exceptionally permitted on the basis that they are designed to induce wrongdoing States into law compliance.Footnote 94 On the face of it, it may seem appropriate to rely on the doctrine of countermeasures to preclude State responsibility for non-forcible responses to armed attacks given that such attacks will usually qualify as unlawful uses of force.Footnote 95 However, while the doctrines of countermeasures and self-defence may overlap insofar as they can apply to the same set of circumstances,Footnote 96 countermeasures will rarely provide a suitable legal mechanism to address non-forcible responses to armed attacks. As will be seen, there are sound conceptual, theoretical and doctrinal reasons why such responses should be characterised as acts of self-defence.
A. Distinguishing the Aims and Objectives of Countermeasures and Self-Defence
Conceptually, the doctrines of countermeasures and self-defence describe different phenomena and serve different aims and objectives. Notwithstanding the global reach of the UN's collective security regime, international law remains a decentralised system and much of its enforcement lies in the hands of those who believe they have been wronged.Footnote 97 The doctrine of countermeasures is therefore a mechanism by which injured States can enforce compliance with international law and protect their legal rights.
Like countermeasures, self-defence is a form of self-help but, unlike countermeasures, self-defence is not a law enforcement mechanism. The purpose of self-defence is to enable States to protect themselves from armed attacks and, as such, it evokes a war-like paradigm.Footnote 98 Consequently, it is conceptually erroneous to describe non-forcible responses to armed attacks as countermeasures. Instead, this type of reaction is more accurately characterised as an act of self-defence.
B. Justifications and Excuses
Theoretically, countermeasures operate as excuses whereas self-defence is a justification. States can raise different types of defences when they are accused of breaching international law and they are typically categorised as justifications or excuses. In essence, the difference between a justification and an excuse is that the former arises from the properties of the act whereas the latter arises from the properties of the actor. Justification defences describe State conduct that is warranted and therefore lawful per se. Excuse defences, on the other hand, concede that the impugned conduct is unlawful but maintain that, given the exigencies of the circumstances, the State is not to blame for its actions and, consequently, legal responsibility should not be assigned.Footnote 99
There is little doubt that the right of self-defence acts as a justification.Footnote 100 The ILC casts self-defence as a primary rule of international law and this means that defensive action does not ‘even potentially’ breach the principle of non-use of force.Footnote 101 As has already been mentioned, the ILC erroneously concludes that self-defence is an exception to the non-use of force principle. But for present purposes, what is important is that the ILC regards self-defence action as inherently lawful due to its very nature. This view is supported by the fact that Article 51 UN Charter describes self-defence as an ‘inherent right’ and, in the equally authoritative French version of this provision, self-defence is referred to as a ‘droit naturel’, that is, a natural right.
Whether countermeasures constitute justifications or excuses is a trickier question because, while self-defence as embodied in Article 51 UN Charter is a primary rule of international law, countermeasures are governed by secondary rules. The ASR identify various defences to the imposition of State responsibility and they are referred to as ‘circumstances precluding wrongfulness’. As circumstances ‘precluding wrongfulness’ the implication is that, when present, the impugned conduct is not unlawful. Given this language, commentators have claimed that the defences enumerated by the ASR (including the doctrine of countermeasures) constitute justifications for the non-performance of international legal obligations.Footnote 102
However, the ILC's use of the phrase ‘circumstances precluding wrongfulness’ is not intended to cast all the defences identified in Chapter V of the ASR as justifications.Footnote 103 This is illustrated by the fact that the Commentary to the ASR expressly states that the circumstances precluding wrongfulness listed in Chapter V can take the form of justifications or excuses.Footnote 104 In its discussion of countermeasures, the ILC avoids taking a firm stance on whether countermeasures are justifications or excuses. The ILC's failure to be pinned down on this issue chimes with the views of Special Rapporteur Crawford when he refers to countermeasures as ‘possibly’ being a justification (rather than an excuse), whereas when discussing other circumstances precluding wrongfulness he is more exact.Footnote 105 Fundamentally, and to emphasise what was said above, it is the nature of the act that determines whether a defence is a justification or an excuse: a defence is a justification when the act is warranted and a defence is an excuse when the act is wrongful but legal responsibility is absolved given the circumstances.
In her study of this topic, Paddeu maintains that countermeasures are justifications on the basis that ‘the wrongdoing State has, by its conduct, forfeited the legal protection of its rights’ and, consequently, the injured State has a Hohfeldian liberty-right to take countermeasures against it.Footnote 106 Understood in this way, countermeasures are lawful ab initio because they do not run into conflict with an operative rule of international law.Footnote 107
A more compelling theory to explain the doctrine of countermeasures begins with the recognition that countermeasures constitute a breach of international law. At the same time, this theory recognises that the State taking countermeasures has had its legal rights breached by the wrongdoing State and, on this basis, it is exceptionally permitted to engage in otherwise unlawful conduct in order to induce the wrongdoing State into compliance with its legal obligations. Thus conceived, it is the properties of the actor—namely, that the injured State has been wronged—that excuse State responsibility for the employment of a countermeasure, rather than the countermeasure being justified on the basis of its internal properties. According to this theory, countermeasures operate as excuses rather than justifications.Footnote 108
For Paddeu, the ‘acid test’ proving that countermeasures are justifications rather than excuses lies in the fact that States rarely request or pay compensation for material loss suffered as a result of countermeasures.Footnote 109 In her view, this proves that countermeasures are justifications because States are not obliged to pay compensation for material loss caused by lawful acts but compensation is due where the act is unlawful and responsibility is excused.
Paddeu is correct that States do not have to provide compensation for justified behaviour because, after all, there has been no breach of international law. However, it is not necessarily the case that States must provide compensation for internationally wrongful conduct for which responsibility is excused. As the ILC explains, there is no hard and fast rule as to whether compensation is owed when a circumstance precluding wrongfulness is established—instead, whether compensation is required is determined on a case-by-case basis.Footnote 110 Moreover, and as will be seen below, the law on State responsibility permits States to take countermeasures that produce irreversible effects where no other option is reasonably available. It is therefore difficult to argue that, where a non-reversible countermeasure is taken as a last resort, the injured State must provide compensation for the material loss caused. In sum, the fact that States do not usually request or provide compensation for material loss does not point inexorably to the conclusion that a countermeasure is a justification rather an excuse.
Why does it matter whether countermeasures are classified as justifications or excuses? For Franck, ‘the distinction between what is justified (exculpated) and what is excusable (mitigated) is so fine as to be of pure (yet also considerable) academic interest’.Footnote 111 The point Franck is making is that, regardless of whether countermeasures are classified as a justification or an excuse, the legal effect is the same: the State will not be held legally responsible for lawfully deployed countermeasures.
While this may be the case, there are nevertheless significant political and legal differences between justifications and excuses. In political terms, the distinction is a ‘fundamental one for moral judgment’ and this has important implications for a State's standing and reputation in the international community.Footnote 112 In short, it is preferable for a State to establish that its conduct is justified and therefore did not involve a breach of international law than to admit that it acted unlawfully but assert that its responsibility is excused given the exceptional nature of the circumstances. This is the point made by Lowe when he explains that the distinction between justifications and excuses ‘is the very stuff of classical tragedy. No dramatist, no novelist would confuse them. No philosopher or theologian would conflate them.’Footnote 113 As will be seen in the following discussion, that a countermeasure is an excuse and self-defence a justification also accounts for important legal differences between these doctrines.
C. The Legal Differences between Countermeasures and Self-Defence
Doctrinally, the legal regimes regulating countermeasures and self-defence differ in a number of important respects. First, where a wrongdoing State breaches the legal rights of an injured State, the latter cannot invite non-injured States to take countermeasures on its behalf in order to protect its legal interests and enforce compliance with international law (a doctrine known as third-party countermeasures).Footnote 114 By contrast, where a State falls victim to an armed attack and engages its right of self-defence, it can request third States to take defensive measures on its behalf against the aggressor State (a doctrine known as collective self-defence).Footnote 115 The rationale for why international law prohibits third-party countermeasures but permits collective self-defence lies in the distinction between countermeasures as an excuse and self-defence a justification.
As has been seen, countermeasures are exceptionally permitted on the basis that the injured State has had its legal rights infringed. Countermeasures are thus personal to the injured State, which means the injured State's right to take countermeasures against a wrongdoing State cannot be passed on or extended to third States. In contradistinction, self-defence action is inherently lawful and a victim State can therefore invite other States to assist in the lawful exercise of its right. As Ohlin explains:
Since justifications are general in nature and negate the wrongfulness of the act, it stands to reason that the justified actor engaging in defensive force has performed no wrongful action in defending himself. If the action itself is not wrongful, then third parties are entitled—by logical extension—to come to the aid of the original victim. In this way, justifications always flow down to third parties, who by definition receive the benefits of the original actor's justification. Excuses, by contrast, do not flow down to third parties.Footnote 116
Secondly, as countermeasures must be designed to induce compliance with international law, it stands to reason that they can be deployed only against those actors who have breached international law, which invariably means States given that they are the principal subjects of international law.Footnote 117 As a result, non-State actors such as armed groups cannot be made the object of countermeasures. Yet, as history shows, non-State armed groups are capable of launching violent attacks against States. Thus, where States resort to non-forcible measures to counter armed attacks by non-State actors, they cannot rely on the doctrine of countermeasures. Crucially, these complications do not arise in the context of self-defence because Article 51 UN Charter permits States to take defensive action against armed attacks irrespective of whether the author is a State or non-State actor,Footnote 118 a position that has been confirmed by the SC and abundant State practice.Footnote 119
Thirdly, countermeasures are available only in response to prior violations of international law.Footnote 120 Hence, it is a misnomer to talk of anticipatory countermeasures. But what about a situation where a State faces an imminent threat of an armed attack and responds with non-forcible measures? In this scenario, countermeasures are unavailable. While there is disagreement among States as to whether self-defence can be engaged against latent, embryonic and emerging threats (a doctrine known as pre-emptive self-defence), it is widely accepted that self-defence can be invoked to avert an imminent threat of an armed attack (often referred to as anticipatory self-defence).Footnote 121 It could be said that an imminent threat of an armed attack constitutes an unlawful threat of force and, as such, a non-forcible response to that attack can be treated as a countermeasure against an internationally wrongful act. This argument is difficult to sustain, however, because Article 51 UN Charter is not a legal rule as such but is instead designed to preserve and affirm the customary right of self-defence where an armed attack occurs. The notion of armed attack therefore describes a factual state of affairs—has a grave use of force been used against the victim State?Footnote 122 Thus, an armed attack does not automatically or necessarily constitute an unlawful use of force,Footnote 123 which means that an imminent threat of an armed attack does not automatically or necessarily constitute an unlawful threat of force.
Fourthly, the law on State responsibility requires States to notify wrongdoing States before countermeasures are commenced,Footnote 124 the rationale being that wrongdoers must be afforded the opportunity to rectify their unlawful conduct and, by bringing their conduct into compliance with international law, obviate the need for countermeasures. Exceptionally, an injured State is permitted to dispense with prior notification where ‘urgent countermeasures’ are ‘necessary to preserve its rights’,Footnote 125 although in this situation the burden falls on the injured State to demonstrate that urgent countermeasures are necessary or, in other words, that prior notification is not an option given the circumstances. Patently, the requirement of notification is unrealistic where a State is responding to an incident that poses a grave threat to its national security, such as where it falls victim to an armed attack. Additionally, when responding to an armed attack, notification is problematic: making aggressors aware that defensive action is about to be undertaken may undermine the effectiveness of the riposte. For these reasons, and unlike countermeasures, the law of self-defence does not require victim States to notify attacking parties that they are about to resort to defensive measures or demonstrate why prior notification is not possible.Footnote 126
Fifthly, ‘[c]ountermeasures shall, as far as possible, be taken in such a way as to permit the resumption of performance of the obligations in question’.Footnote 127 The expectation, then, is that the effects of countermeasures are reversible,Footnote 128 and the reason for this is because the purpose of countermeasures is to restore the legal status quo. But as the ILC explains, the effects of countermeasures must be reversible ‘as far as possible’ or, said differently, ‘the duty to choose measures that are reversible is not absolute’.Footnote 129 This means that, if a range of countermeasures is available and each would be equally effective in pushing a wrongdoing State into complying with its legal obligations, the injured State must opt for the countermeasure that is reversible. If only non-reversible countermeasures would be effective, they can be deployed but it is incumbent upon the injured State to demonstrate that it was not possible to select a countermeasure with reversible effects. When it comes to self-defence, there is no requirement that the effects of defensive measures are reversible.
Sixthly, and as has been seen, the doctrines of countermeasures and self-defence are subject to the principle of necessity: countermeasures must be necessaryFootnote 130 to induce compliance with international law and acts of self-defence must be necessaryFootnote 131 to halt and repel an armed attack. Moreover, countermeasuresFootnote 132 and acts of self-defenceFootnote 133 must be proportionate to meeting these objectives. Importantly, the principle of proportionality takes on a different meaning in the context of countermeasures than it does with self-defence.
With regard to countermeasures, the principle of proportionality requires that the response ‘must be commensurate with the injury suffered, taking into account the gravity of the internationally wrongful act and the rights in question’.Footnote 134 To ensure that an appropriate balance is struck between the harm sustained and the harm inflicted, the proportionality principle requires a qualitative assessment of the rules and rights breached by the countermeasure as well as a quantitative assessment of the harmful effects produced.Footnote 135 While countermeasures do not have to be identical to the wrongful act to which they respond, there must be ‘equivalence’Footnote 136 between them and countermeasures are disproportionate where the harm caused is ‘excessive’ when compared to the harm sustained.Footnote 137
When it comes to measuring the proportionality of self-defence, some commentators maintain that this principle requires a quantitative assessment of the harm caused by the defensive action. In short, their argument is that defensive action is disproportionate where the harm inflicted (on the target State, third States, civilians, the environment, etc) goes beyond what is needed to repulse the armed attack.Footnote 138 However, this interpretation of the principle of proportionality is not supported by State practice.Footnote 139 Whether the harm caused by defensive action is within permissible limits is not regulated by the jus ad bellum principle of proportionality, but instead determined by other international law regimes such as international humanitarian law and international human rights law. In the ad bellum context, the only restriction imposed by the principle of proportionality is that victim States do no more than achieve the specific objective of defending themselves. Thus, providing the riposte is designed to achieve self-defence—which is established where there is a ‘rational connection’Footnote 140 between the defensive action and repelling the attack—the principle of proportionality is satisfied.
Whether a rational connection exists is invariably answered by the principle of necessity insofar as it requires that defensive action must be necessary to attain self-defence or, in other words, defensive action must be undertaken as a ‘last resort’ to halt and repel an armed attack.Footnote 141 In practice, then, when it comes to the law of self-defence the principles of necessity and proportionality converge and ‘are truly two sides of the same coin’.Footnote 142 This means that the principle of proportionality in the context of the law on countermeasures is more demanding than the principle of proportionality under the law on self-defence, and the reason for this is because countermeasures are exceptional measures designed to restore law and order within the international community whereas self-defence is an inherent right of victim States to defend themselves against grave violence.
V. Conclusion
Rejecting conventional wisdom, this article has demonstrated that self-defence is a general right under international law and, as such, permits States to take all measures necessary to counter an armed attack regardless of whether they amount to a threat or use of force. This article has presented the doctrinal evidence to support this claim. Prior to the signing of the UN Charter, State practice revealed an acceptance within the international community that the right of self-defence permitted recourse to non-forcible and forcible measures. Through customary and treaty law, States have placed strict limits on when the right of self-defence can be engaged. At no point, however, have States restricted the right of self-defence to the use of forcible measures exclusively. As has been seen, neither the text of Article 51 nor the structure of the UN Charter limits the right of self-defence to forcible measures. Moreover, State practice on Article 51 confirms that the right of self-defence can be invoked to justify all measures necessary to fight off an armed attack.
Countermeasures and self-defence are distinct legal doctrines insofar as they are triggered by different events and subject to their own conditions and restrictions. This article has argued that, while there may be circumstances in which a non-forcible response to an armed attack may satisfy the conditions necessary to engage the doctrine of countermeasures, there are important conceptual, theoretical and doctrinal reasons why such a response should be characterised as an act of self-defence (provided, of course, that it meets the other treaty and customary conditions required by the law of self-defence). Fundamentally, the reason why there are such significant differences between these doctrines lies in the fact that countermeasures are responses to illegality (and thus law enforcement mechanisms) whereas self-defence is a response to grave violence (and thus an act of self-preservation).
Since the establishment of the UN in 1945, there have been various attempts to expand the right of self-defence.Footnote 143 For example, there have been claims that any unlawful use of force constitutes an armed attack and therefore engages the right of self-defence,Footnote 144 and that the right of self-defence can be invoked pre-emptively to counter emerging or embryonic threats.Footnote 145 Rightly so, efforts to broaden the law of self-defence have given rise to considerable apprehension within the international community.Footnote 146 The reason for this is because the right of self-defence usually operates as a justification for measures that would be otherwise internationally wrongful and, consequently, an overly broad reading of this doctrine risks undermining respect for international law. Moreover, an expansive reading of the right of self-defence confers on States greater latitude for unilateral action, which risks sidelining the UN's collective security system notwithstanding the fact that, as has been seen, the SC can always suspend the right of self-defence by taking measures necessary to restore international peace and security.
Some may argue that interpreting the right of self-defence to include non-forcible measures represents another attempt to expand its application beyond acceptable limits, and to do so would further challenge the authority of international law and the centrality of the UN's collective security system. These concerns are misplaced. Regardless of whether a State deploys forcible or non-forcible measures to fight off an armed attack, it must be emphasised that all types of defensive action are subject to the law of self-defence's well-established restrictions: self-defence must be in response to an armed attack; defensive measures must be necessary and proportionate in the circumstances; invocations of self-defence must be reported to the SC; and the right of self-defence is suspended as soon as the SC takes measures necessary to maintain international peace and security. These restrictions circumscribe the deployment of defensive non-forcible measures in the same way and to the same extent as they circumscribe the use of defensive forcible measures. Ultimately, these restrictions ensure that the law of self-defence maintains an appropriate balance between preserving the inherent right of States to defend themselves from armed attack and preventing unilateral action that undermines respect for the international rule of law.
In fact, accepting that self-defence permits the use of non-forcible measures may even have a de-escalatory effect on hostilities. Consider, for example, a situation where a State falls victim to an armed attack and determines that non-forcible measures would be effective at halting and repelling it. If the law of self-defence does not permit a victim State to resort to non-forcible measures, its only option may be to use force and, by doing so, run the risk of unnecessarily escalating the crisis. A reading of the law of self-defence that permits the use of non-forcible as well as forcible measures is therefore sound as a matter of international law and policy.
