Duality of Responsibility in International Law: The Individual, the State, and International Crimes. By Thomas Weatherall. Leiden: Brill Nijhoff, 2022. 367 + xxxiv pages.

On 20 May 2024, Karim Khan KC, the prosecutor of the International Criminal Court (ICC), announced that his office had filed applications for arrest warrants against the leadership of Hamas and the prime minister and secretary of defence of the state of Israel for suspected war crimes and crimes against humanity committed in Gaza after 7 October 2023. ¹ Just a couple of miles away, the International Court of Justice (ICJ) was deliberating on its fourth order on provisional measures in the case instituted by South Africa against the state of Israel claiming violations of the Genocide Convention against the people of Gaza in the same period. ² Parallel international proceedings against states and individuals are also currently pending before the ICJ and the ICC with respect to allegations of crimes under international law committed against the Rohingya people in Rakhine State, Myanmar, ³ as well as against civilians in the course of the war in Ukraine. ⁴ In the past, different international courts and tribunals have dealt with applications against states and criminal charges against individuals — most notably, with respect to the Yugoslav war. ⁵ It is firmly established within the current framework of international law that the commission of certain acts –– most notably, genocide –– triggers the international (and domestic) responsibility of states and individuals simultaneously. ⁶ According to the ICJ, this “duality of responsibility continues to be a constant feature of international law.” ⁷ What is less established or constant is what this duality entails for the operation and evolution of the respective international responsibility regimes and, concomitantly, for the bureaucracies tasked with their implementation.

Thomas Weatherall’s Duality of Responsibility in International Law draws upon this broader theme. It interrogates the relationship of the international responsibility of states and individuals as it has been portrayed in broad strokes by the ICJ:

State responsibility and individual criminal responsibility are governed by different legal régimes and pursue different aims. The former concerns the consequences of the breach by a State of the obligations imposed upon it by international law, whereas the latter is concerned with the responsibility of an individual as established under the rules of international and domestic criminal law, and the resultant sanctions to be imposed upon that person. ⁸

The main premise of this book is that certain primary rules of international law apply to both states and individuals, giving rise to duality of responsibility. ⁹ As such, “secondary rules governing individual and state responsibility come into contact as they operationalize duality of responsibility, which in many instances may be observed to impact their application in ways that are unique to the primary rules that give rise to such duality.” ¹⁰ Against this backdrop, the book provides a detailed description of those secondary rules and maps how they interact with a view to identifying “convergence in the international law of dual responsibility.” ¹¹

The scope of the mapping exercise carried out by Weatherall is extensive. Part 1 lays down the theoretical premises of the work comprising the capacity of both states and individuals to incur international responsibility (Chapter 1) and the distinction between primary and secondary rules of international law as they apply to states and individuals (Chapter 2). Part 2 examines under the rubric of “breach” the elements of crimes under international criminal law (Chapter 3), the elements of the internationally wrongful act under the law of state responsibility (Chapter 4), and their ensuing interaction including at the level of sources of international law and applicable standards of proof (Chapter 5). Part 3, titled “Attribution,” discusses the different modes of liability under international criminal law (Chapter 6) and the rules of attribution of conduct under the law of state responsibility (Chapter 7) as well as the implications of double attribution of conduct to states and individuals for the operation of the international law on immunity of state officials (Chapter 8). Part 4, titled “Responsibility,” discusses the content of responsibility under the respective regimes (Chapter 9), the available defences (Chapter 10), as well as the issues of jurisdiction (Chapter 11) and immunity and inviolability (Chapter 12). Part 5 highlights the key findings of the inquiry along the three axes of breach, attribution, and responsibility (Chapters 13 and 14).

The resulting map depicts a vast “shared legal space” between state responsibility and individual criminal responsibility under international law. ¹² What marks the boundaries of Weatherall’s inquiry is the distinction between primary and secondary rules. ¹³ Weatherall uses a broad notion of secondary rules that includes not only the international law of state and individual responsibility but also “associated” secondary rules, including the rules on jurisdiction and immunity. ¹⁴ While this expansion appears deliberate, its practical value is open to question. For instance, the chapter on jurisdiction primarily outlines the available fora for prosecuting individuals and presents the basic rules for adjudicating disputes between states, ultimately designating this area as one of “divergence.” ¹⁵ Similarly, the chapter on immunities mainly records the practice of international criminal courts rejecting claims of immunity and that of domestic courts affirming the immunity of states and its most senior officials with respect to the alleged violations of the primary norms covered in the study. ¹⁶ The chapter also expands upon the still contested issue of functional immunity (ratione materiae) of state officials from foreign criminal jurisdiction for crimes under international law, though much of this discussion largely mirrors the analysis provided earlier in the chapter on attribution. ¹⁷ One may also wonder if this expansion sacrifices a degree of detail. For example, the chapters on jurisdiction and immunities treat all alleged violations of primary rules entailing dual responsibility in a largely uniform manner, without considering the possibility that differences may exist in how certain violations may be treated. The crime of aggression is a case in point. ¹⁸

To its credit, the book refrains from imposing any comprehensive normative agenda on its reader. Weatherall, who is more committed to his quasi-cartographic methods than to his stated goal of contributing to convergence between the two regimes, ¹⁹ does not shy away from designating large areas in the law of state and individual responsibility as points of divergence. ²⁰ At the same time, a roadmap is as good as its landmarks. The inclusion of both the material and mental elements of crimes under international law and of the internationally wrongful act under the same rubric of “breach” seems somewhat misplaced, notwithstanding precedents in literature. ²¹ The two concepts operate at different levels of abstraction. Breach is only an element of an internationally wrongful act of a state. ²² Moreover, analytically speaking, the material and mental elements of crime are not sufficient conditions to establish individual criminal responsibility; it is also necessary to determine that a specific mode of liability applies to the specific accused. ²³ Similarly, the grouping of modes of liability under international criminal law and the rules of attribution of conduct under the law of state responsibility within the same heading of “attribution” masks profound differences about the scope and purposes of the underlying juridical operations, even within the rules under discussion. What exactly is being attributed under the rules of individual criminal responsibility and what under those of state responsibility?

This issue goes beyond mere terminology. First, one of the book’s recurring claims is that state responsibility is “subsidiary” to individual criminal responsibility or that it operates “successively” to individual criminal responsibility. ²⁴ Weatherall states that “international criminal conduct is sufficient to satisfy the element of breach of an international obligation for the state,” while “[i]t is practically unlikely for the breach of an obligation by the State to serve as the basis for a subsequent determination of an individual criminal responsibility.” ²⁵ While the claim offers a straightforward narrative, it remains largely unsubstantiated. In fact, it appears to contradict the premise of the book that the same primary rules apply to both states and individuals. ²⁶ Similarly, the analysis on applicable standards of proof in inter-state and international criminal proceedings does not appear to fully support this claim. ²⁷ Furthermore, Weatherall acknowledges that the crime of aggression might upset this configuration because the establishment of a state act of aggression is an element of the crime. ²⁸ Less obviously, the claim about the subsidiarity of state responsibility also overlooks the fact that establishing individual responsibility in international criminal law is a two-step process. For example, modes of liability in international criminal law include “leadership modalities” that encompass the commission of all crimes under international law through organizations, including, conceivably, the state apparatus or some parts of it. ²⁹ In this context, the characterization of a course of conduct as a breach of an international obligation by a state –– that is, the prohibition of genocide, crimes against humanity, or war crimes –– is just as likely to inform the establishment of individual criminal responsibility as a practical matter. However, the relevant chapter (Chapter 6) does not delve into these nuances or reflect on the relevant practice of international criminal courts and tribunals.

Second, the conflation of two distinct juridical operations ––attribution of conduct and attribution of responsibility –– leads to the conclusion that the two regimes diverge due to the centrality of the principle of culpability in international criminal law and the “objective” character of state responsibility. ³⁰ However, by addressing the issue of mental elements exclusively from the perspective of secondary rules, Weatherall neglects the connection between secondary rules and primary rules binding on states. ³¹ In the context of the establishment of a breach of an international obligation as a necessary condition for attributing responsibility to a state, obligations that are addressed both to states and individuals include mental elements. ³² Less conspicuously, when the general rules of state responsibility attribute responsibility to a state, as they do with respect to internationally wrongful acts of other states or international organizations, they tend to include mental elements. ³³ Whilst Weatherall appears to recognize the potential of interaction between these concepts, ³⁴ he concludes that “it is unclear how … [it] may or may not impact the attribution to the State of conduct engaging individual criminal responsibility for aiding and abetting an international crime.” ³⁵ Arguably, this complexity deserves a more detailed account and thoughtful evaluation. ³⁶

Besides, a crucial choice when making a map is what detail to include in the map and what to leave out. ³⁷ To illustrate this point, in one notable instance, the book concludes that the two regimes of responsibility pursue different purposes, ultimately echoing the dictum of the ICJ, despite initially aiming to challenge it. ³⁸ Weatherall asserts that the purpose of individual responsibility in international law is retribution and deterrence and, thus, only encompasses punitive consequences. ³⁹ What is most notable is that the book overlooks the possibility that individual responsibility under international law has also a “restorative” purpose. ⁴⁰ One obvious example of this aspect is the obligation of individuals to make reparation for the harm caused by their crimes under international law, ⁴¹ a topic that Weatherall has explored extensively in his previous work. ⁴² Unfortunately, there is no explanation provided for that omission in his work under review.

It is important to acknowledge that presenting a comprehensive academic work in the form of a book review risks overshadowing the author’s narrative and achievements with the reviewer’s expectations and biases. Weatherall’s work intervenes in a densely populated legal space that often appears dangerously compartmentalized and suspiciously static. His normative vision of an international law of dual responsibility is undoubtedly compelling. However, to this reviewer, it remains questionable whether the book fully achieves this ambitious agenda or reinforces, perhaps inadvertently, existing doctrinal and institutional silos.