This chapter reviews the enforcement of IHL through a range of legal and non legal mechanisms. It first addresses the obligation to respect and ensure respect for IHL, protecting powers, the international humanitarian fact finding committee and the role of human rights bodies. State responsibility, state immunity and acts of state and political question doctrines are then discussed. Reparations, including state reparations, individual reparations and reparations by armed groups are then reviewed. UN immunity, UN enforcement and responsibility in peacekeeping operations, liability and reparations in peacekeeping operations and criminal responsibility in peacekeeping operations are also addressed. The use of belligerent reprisals in the enforcement of IHL and armed groups and enforcement of IHL is then discussed. In conclusion the chapter considers United Nations Action in enforcement of IHL.

Under international criminal law (‘ICL’), individuals can be prosecuted and punished for conduct that is criminalised under customary international law and/or treaty. This differs from most branches of international law, which concern the rights and obligations of states. The rationale for holding individuals to account for such crimes was articulated in 1946 by the International Military Tribunal at Nuremberg, which stated: ‘Crimes against international law are committed by [people], not by abstract entities, and only by punishing individuals who commit such crimes can the provisions of international law be enforced.’ This chapter introduces this branch of international law, citing examples involving Australia as well as many other states. The chapter gives an overview of some of ILC’s key principles and aims, andoutlines the historical development of ICL. It explains how ICL is currently being enforced, considers the core crimes in ICL and discusses individual criminal responsibility and defences.

Chapter 7 explores the application of the individual criminal responsibility rules to the facts of individual cases at the International Criminal Court (ICC). It looks at the facts and evidence presented by the prosecutor, as well as the conclusions of the judges at the pre-trial and trial stages of proceedings, to ask whether the requirements of the Rome Statute’s modes of liability are met. In view of the practices of the UN tribunals, many members of the international criminal justice community expected that the ICC judges would apply the Rome Statute in a manner that would render convictions easier. Instead, this chapter argues that the assessment of criminal responsibility at the Court has followed a different line of legal reasoning: applying the modes of liability in a restrained manner, regardless of the trial outcome. At the ICC the quality of the process has been cherished as the ultimate prerequisite for ‘ending impunity’ for those crimes. While this vision of international criminal law has been contested by some members of the international criminal justice field, such as human rights advocates, it has continued to dominate the ICC approach to assessing criminal responsibility.

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 1 situates Responsibility on Trial within the existing interdisciplinary literature on international criminal justice and presents the research aims of the book. Chapter 1 highlights a gap in the existing literature: international criminal law norms are generally treated either as objective and static standards that are independent from states’ political interests (the ‘liberal-legalist’ thesis), or, conversely, as inevitably indeterminate concepts that enable the perpetuation of global structural inequalities (the ‘critical’ thesis). While both perspectives provide important insights into the operation of international criminal justice, they fail to examine the dynamic nature of legal norms as vehicles for both continuity and change in the field and the implications of those dynamics for the assessment of individual criminal responsibility for mass atrocities. To address this gap, Chapter 1 borrows insights from the work of Shklar and Kirchheimer and proposes building an ‘intersubjective’ framework of analysis that recognizes law’s inherent normativity not as an objective fact but as a form of social practice.

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.

Chapter 2 counters each of the policy arguments that have been mounted against the criminalisation of State acts of aggression, including arguments relating to uncertainties surrounding the prohibition of the use of force; that acts of aggression are too complex an episode for adjudication by a criminal tribunal; that the criminalisation of aggression will politicise the ICC; that there is a risk of a fragmentation of relevant rules of international law caused by differing decisions of the ICC, the UN Security Council, and the International Court of Justice; and claims that the criminalisation of acts of aggression will have a chilling effect on States’ willingness to use force when they should (namely, to prevent atrocity crimes). The dissection of such arguments demonstrates that each objection is misguided and sets out the case in favour of criminalisation. The chapter also assesses the geopolitical significance of the crime, considering the extent to which the criminalisation of the unlawful use of force represents a shift in the balance between power and law. Finally, the chapter examines the likely impact of the crime of aggression on the rules of the jus ad bellum.

Hans Kelsen’s interventions in the law of the Nuremberg trials have remained unexplored with the exception of notes in passim or a couple of brief studies. International criminal law, is true, was not Kelsen’s main object of study. However, the events culminating in Nuremberg, both the shocking Nazi policies and that Kelsen was an émigré in the United States were instrumental to precipitate his close engagement with international criminal law during the dawn years between 1942 and 1945. This chapter introduces the man and his ideas, traces elements of the pure theory that relate to the principle of individual criminal responsibility and, with the help of hitherto unknown archival material, describes for the first time Kelsen’s personal participation in the preparations of Nuremberg and the history behind his absence from the International Military Tribunal. The chapter concludes with a selection of two aspects of Kelsen’s activities as a legal advisor for the US War Crimes Commission: first, his insistence on the need for an international treaty as the legal basis of the IMT in order to avoid victors’ justice and problems of jurisdiction; second, his contribution towards the inclusion of individual criminal responsibility in the London Agreement.