The final substantive chapter of the book looks at how all these rules are implemented and enforced, and what mechanisms exist to hold violators of the law accountable for their acts. Common Article 1 of the Geneva Conventions requires states to ‘ensure respect’ for the rules of IHL, which is achieved through a range of measures such as education of the armed forces and civil society in the rules of IHL and entrenching the rules in domestic legislation. The chapter describes the roles of the ICRC, Protecting Powers and the International Humanitarian Fact-Finding Commission. The development and content of international criminal law are examined, including individual responsibility for war crimes, lesser violations of IHL, crimes against humanity and genocide, and the concept of command responsibility is explained. The growth in international and hybrid criminal tribunals is noted, as well as the roles played by the United Nations and other organisations in encouraging adherence to the rules of IHL. Finally the chapter examines mechanisms for implementation, enforcement and accountability in non-international armed conflict.

Chapter 6 argues that the competition for delivering an authoritative interpretation of the criminal responsibility provisions in Article 25(3), Article 28, and Article 30 Rome Statute continued when the International Criminal Court (ICC) began operation. This chapter shows that the interpretation of Article 25(3) should be understood not only as an indication of the growing influence of civil law norms, as has been often suggested in the legal literature, but also with respect to other important overlapping factors, namely the growing dissatisfaction with joint criminal enterprise and the novel institutional environment of the ICC. Next, Chapter 6 observes that the ICC judges have interpreted in a very restrained manner Article 28 and Article 30, perhaps going beyond the intentions of the Rome Statute drafters. This chapter provides a comprehensive analysis of the (re)construction of criminal responsibility rules at the ICC over a period of 15 years, including recent developments, which took place in 2020–2021 in the Yekatom and Ngaïssona, Abd-Al-Rahman and Said cases, thus highlighting the dynamic nature of international criminal law norms.

Chapter 4 argues that the nascent community of international criminal law practice coalesced around the judgments issued by the International Military Tribunal (IMT) in Nuremberg and International Military Tribunal for the Far East (IMTFE) in Tokyo after the end of the Second World War. The United Nations (UN) tribunals for the Former Yugoslavia (ICTY) and Rwanda (ICTR), established in the 1990s, significantly developed the legal rules regulating the attribution of individual criminal responsibility for mass atrocities, further consolidating the international criminal justice field. Chapter 4 argues that, from the perspective of intersubjective legalism, both the post-Second World War tribunals and the UN tribunals displayed sound legal reasoning in the assessment of criminal responsibility for two reasons: Firstly, they followed a consistent normative logic, namely that morality was the animating force behind legality. Secondly, many judges and outside legal commentators shared that normative logic. Nevertheless, over time the UN tribunals polarized the international criminal justice community of practice on questions concerning the scope and requirements of criminal responsibility rules.

Chapter 5 offers new insights into the drafting of the criminal responsibility rules in the Rome Statute. Specifically, the chapter argues that it would be simplistic to present the restrained approach to the assessment of criminal responsibility exhibited in the Rome Statute as the triumph of sovereign states, seeking to shield their nationals from convictions, over non-state actors, such as legal scholars, and non-governmental organizations, aiming to expand the scope of criminal responsibility provisions to enable easier convictions for the perpetrators of mass atrocities. In fact, authoritative legal experts were among the most ardent proponents of the proposal to codify in detail the general principles of criminal responsibility in the RS, instead of granting discretion to the future judges at the Court to develop the rules of criminal responsibility. From the perspective of those legal experts, the inclusion of a ‘General Part’ in the Statute marked the progress that ICL had made since its early days towards a coherent penal system. Thus, the politics of the legal field, that is, the promotion and contestations of different understandings of the law, are crucial for understanding how the principled approach to criminal responsibility became influential in Rome.

The trial of Jean-Pierre Bemba grew out of a separate fact situation in the Central African Republic (CAR). Bemba was a powerful politician on the Congolese national stage, and was also the leader of an armed rebel force, a part of which had been sent across the border in a vain effort to halt a coup against the CAR President. Bemba’s men were accused of widespread crimes against civilians, including sexual crimes against both women and men. The trial tested a theory of criminal responsibility intended for remote commanders who fail to prevent or punish crimes on the ground. Although Bemba was convicted on this basis and sentenced to eighteen years' imprisonment, two years later his convictions were overturned by a bold Appeals Chamber majority. At stake on appeal were fair trial concerns about the need for greater specificity in criminal charges, which led the divided appeals panel to debate the meaning of core legal principles. Looking back to earlier judicial controversies, reversals, dissents, and acquittals, the dialogue surrounding Bemba’s successful appeal identified key questions for future judges to ponder.

Chapter 10 looks at command responsibility, the other side of the “obedience to orders” coin. A soldier who knowingly obeys an unlawful order is guilty of the resulting crimes but the superior who gave the order is equally culpable. Like obedience to orders, command responsibility is an ancient concomitant of command authority. The modern establishment of command responsibility arguably started with the case of Japanese General Yamashita, at the end of World War II. His military commission ruled that, although he issued no unlawful order, he knew or should have known of the crimes being committed by his subordinates. He was hanged for his inaction. Nazi generals were hanged or imprisoned for orders they issued or passed on. The commander’s knowledge, actual or constructive, is required for conviction. A commander’s seven routes to trial – the ways in which a combatant leader may be exposed to legal liability for their subordinates’ actions – are explained and illustrated by modern-day cases. The chapter also recites instances of officers themselves disobeying orders they view as unlawful. Today, 1977 Additional Protocol spells out a commander’s responsibility for unlawful acts.

Chapter 4 brings the student fully into today’s LOAC with details of 1977’s Additional Protocol I and Protocol II. It explains why there was a need to update the 1949 Geneva Conventions and why A.P.s I and II, initially favored by the US, turned out not to be what the US and her allies had anticipated. There were positive changes and additions in both Protocols, as well as regrettable LOAC modifications. Both sides of that coin are examined, with discussion of the lasting results of both the positive and negative changes. It is significant to note that US self-interest did not always prevail, and to explain the basis of that lack of international consensus. Relaxing the requirements for prisoner of war status continues to block US ratification of either Protocol. In the A.P. negotiations the US paid a price for its somewhat ill-advised Vietnam venture but America has, by and large, learned to live with the AP I and II provisions it initially fought. Additional Protocol III (2005), far less significant than the earlier Protocols I and II, is also discussed, if briefly.

Chapter 5 examines the individual conduct elements of the crime of aggression, namely ‘the planning, preparation, initiation or execution, by a person in a position effectively to exercise control over or to direct the political or military action of a State’. It considers the extent to which this language makes the crime of aggression a ‘leadership’ crime.Also examined is the individual contribution that must be made by an accused in order to reach a conclusion that an individual has ‘committed’ a crime of aggression, in particular the meaning of the terms ‘planning’, ‘preparation’, ‘initiation’, and ‘execution’, as well as the relevant mental elements. The interaction of the leadership requirement with Rome Statute provisions relating to superior orders and the responsibility of commanders and other superiors is discussed, as is the relevance of the defences of mistake of fact and mistake of law. Finally, the chapter considers the different modes of liability that attract individual criminal responsibility under Article 25(3) of the Rome Statute and whether it is theoretically possible for a leader to order, aid, abet, or attempt a crime of aggression.

This chapter examines how existing laws can and should apply to emerging technology through attribution of responsibility. Legal systems typically seek to deter identifiable persons – natural or juridical – from certain forms of conduct, or to allocate losses to those persons. Responsibility may be direct or indirect: key questions are how the acts and omissions of AI systems can and should be understood. Given the complexity of those systems, novel approaches to responsibility have been proposed, including special applications of product liability, agency, and causation. More important and less studied is the role that insurance can play in compensating harm but also structuring incentives for action. Another approach is to limit the ability to avoid responsibility, drawing on the literature on outsourcing and the prohibition on transferring certain forms of responsibility – most notably the exercise of discretion in the public sector.

At this moment, the literature and discourse on command responsibility is incredibly convoluted and controverted. I will show how these knots were produced by an underlying inadvertent contradiction with the culpability principle. The contradiction was created by surface-level doctrinal reasoning that did not adequately consider the deontic dimension. The subsequent twists and turns to deny, obscure, evade, or resolve this contradiction have led to increasingly complex and obscure claims about command responsibility.

The inquiry demonstrates the problems of inadequate attention to deontic limits. It also shows how deontic analysis can help us better understand the trajectory of the command responsibility debate. We can see old controversies in a new light and generate new prescriptions. I argue that command responsibility can be restored to its simple and elegant origins if it is recognized as a mode of accessory liability. As a result, the causal contribution requirement should be respected. This solution is not perfect, but I will show that this is the best reconciliation of the text, precedents, and the culpability principle. By resolving the core contradiction, the myriad complications and mystical evasions about command responsibility become unnecessary.

This chapter introduces the context and objectives of the book. International criminal law is still a relatively new body of criminal law, that was constructed in a rapid transnational conversation. The time is ripe for careful systematic and normative evaluation of this corpus of law. For example, scholars have noted that some doctrines may contradict fundamental principles of justice that the system claims to uphold. The book proceeds in three steps: it explains a problem, it outlines a solution, and then it demonstrates the solution through application.

The first, preliminary, objective of the book is to demonstrate a problem. Namely, the book highlights the need for an additional type of reasoning in criminal law: ‘deontic’ reasoning, which is different from doctrinal or teleological reasoning, and engages directly with principled constraints such as the legality and culpability principles.

Second, the book outlines a method for deontic reasoning, and in particular for identifying fundamental principles. ICL poses several special challenges for identifying the appropriate principles. The book advances a liberal, open-minded, humanistic, and coherentist approach (and explains each of these features).

Third, the book dissects current controversies in command responsibility in order to demonstrate the method, its questions, and the insights it can generate.

In this chapter, I outline how the approach I have can raise new questions, both for ICL and for general criminal law theory.

The study of extreme cases can unsettle and refine our understandings of the principles developed in everyday experience. I will show how studying ICL problems may require us to unpack the roles traditionally played by ‘the State’ in criminal law thinking, and to re-examine many familiar tools of criminal law thought (such as ‘community’, ‘citizenship’ and ‘authority’). The criminal law theory of ICL might draw on ‘cosmopolitanist’ scholarship, which contemplates forms of governance other than the state, and which is therefore particularly challenging for mainstream criminal law thinking.

I will also highlight ‘promising problems’ in ICL. Exploring such problems can help us refine ICL doctrines and also make contributions to mainstream criminal law theory. These include: legality without a legislature; a humanistic account of duress and social roles; and superior orders and state authority. I will then do an even deeper delve into a selected set of controversies in Chapters 6 to 8, in order to demonstrate the method at work and thereby clarify the method, the work it can do, and the themes it raises.

In this chapter, I move on to resulting normative questions about the culpability principle, causal contribution, and command responsibility. I engage in deontic analysis of what type of contribution the culpability principle actually requires, and whether the requirement might be reconceived.

First, I will examine why criminal law requires causal contribution, and the degree of contribution required. I will argue that the requirement in relation to accessories is not onerous; ‘risk aggravation’ satisfies the culpability principle.

Second, I consider ambitious proposals to re-imagine culpability, i.e. to develop a new deontic account that does not require any causal contribution. A theme of this book is that ICL can present us with new questions that can lead us to adjust our basic assumptions from criminal law theory. On this issue, however, although the arguments are intriguing, my conclusion is that on a coherentist all-things-considered judgement, they are as yet far too tentative and undeveloped to provide a convincing basis for criminal sanctions. Accordingly, the current best theory is that accessories must at least elevate the risk of the crimes occurring.

The trial of Jean-Pierre Bemba grew out of a separate fact situation in the Central African Republic (CAR). Bemba was a powerful politician on the Congolese national stage, and was also the leader of an armed rebel force, a part of which had been sent across the border in a vain effort to halt a coup against the CAR President. Bemba’s men were accused of widespread crimes against civilians, including sexual crimes against both women and men. The trial tested a theory of criminal responsibility intended for remote commanders who fail to prevent or punish crimes on the ground. Although Bemba was convicted on this basis and sentenced to eighteen years' imprisonment, two years later his convictions were overturned by a bold Appeals Chamber majority. At stake on appeal were fair trial concerns about the need for greater specificity in criminal charges, which led the divided appeals panel to debate the meaning of core legal principles. Looking back to earlier judicial controversies, reversals, dissents, and acquittals, the dialogue surrounding Bemba’s successful appeal identified key questions for future judges to ponder.

The primary source of law before the Court is the Statute itself and the principal subsidiary instruments, the Elements of Crimes and the Rules of Procedure and Evidence. The Court may also refer to relevant rules of international law, notably those of international humanitarian law and international human rights law. Article 25 of the Statute sets out the various forms of participation in crimes starting with direct perpetration but also including ordering and forms of complicity and attempt. Article 28 defines so-called command or superior responsibility, by which an individual may be held responsible for crimes perpetrated by subordinates. The Court cannot prosecute an individual who was under 18 at the time of the crime. Statutory limitation of crimes within the Court’s jurisdiction is prohibited. There is a presumption that all crimes subject to the Court’s jurisdiction require proof of intent and knowledge. Several defences are codified: diminished mental capacity, voluntary intoxication, self-defence, duress and necessity, mistake of law and mistake of fact and, under limited circumstances, superior orders.