The definition of the crime of aggression in Article 8 bis of the Rome Statute of the International Criminal Court (Rome Statute) stipulates that a State act of aggression is a material element of the crime, suggesting an intrinsic link between individual criminal responsibility and State responsibility for aggression. This article argues that the Rome Statute provides a legal basis for the International Criminal Court (ICC) to determine State responsibility for aggression when considering the material elements of the crime of aggression, which has important practical and conceptual implications for the law of international responsibility. Although the content of State responsibility flows automatically from the breach of the obligation, it is argued that a finding of aggression pursuant to Article 8 bis of the Rome Statute may be considered as a form of satisfaction for the purposes of Article 37 of the 2001 ILC Articles on Responsibility of States for Internationally Wrongful Acts (2001 ILC Articles). Furthermore, the material element of the crime in Article 8 bis of the Rome Statute requires the act of aggression by its character, gravity, and scale to constitute a manifest violation of the Charter of the United Nations, in line with the nomenclature used within the 2001 ILC Articles regarding serious breaches of obligations arising from peremptory norms of general international law (jus cogens). The article considers the important role that the ICC may play in relation to serious breaches of the jus cogens obligation to refrain from an act of aggression.

To adjudicate a claim on individual criminal responsibility, the court has to establish objective and subjective links between the individual and the crime. This article studies the material (actus reus/objective) elements of the crime of aggression (conduct, consequence and circumstance) and suggests a reading that solves most of the conceptual and practical issues regarding criminal responsibility for this crime. The main contribution is an ontological distinction between the material act of use of violence and the act of aggression, which are both subsumed under the term ‘state/collective act’. The former is a consequence element and therefore is to be understood in its naturalistic meaning – a perceivable result of one’s action. The latter is a legal-evaluative notion and as such constitutes a circumstance that renders the violation of the prohibitory norm (the union of conduct and consequence) as being wrongful. This distinction is crucial for the system of attribution of criminal responsibility, as different mental (subjective) elements apply to consequences and circumstances.

What will be the consequences of the criminalization of aggression? In 2010, the International Criminal Court made aggression a crime for which individuals can be prosecuted. But questions around what constitutes aggression, who decides, and, most important, how effective this legal change will be in reducing the incidence of war remain. This essay considers these questions in light of two recent books on the criminalization of aggression: Noah Weisbord's The Crime of Aggression: The Quest for Justice in an Age of Drones, Cyberattacks, Insurgents, and Autocrats and Tom Dannenbaum's The Crime of Aggression, Humanity, and the Soldier. While the authors argue in favor of the efficacy of the criminalization of aggression as a means to reduce future war, it is also likely that the criminalization of aggression will reshape war in potentially profound ways.

Peter Kooijmans' inquiry into the doctrine of the legal equality of states and, with it, the foundations of international law, reflects a peculiar brand of cosmopolitan thought, namely innate cosmopolitanism. Though under-recognized, innate cosmopolitanism is an argument for re-conceiving the modern international legal order according to a deep unity underlying the whole of human relations. As such, innate cosmopolitanism is distinct from better-recognized examples of cosmopolitan thinking, including liberal cosmopolitanism and cosmopolitan constitutional theory. Rejecting the normative individualism of liberal cosmopolitanism, and eschewing the formal orientation of constitutional theory, innate cosmopolitanism envisions the world as a viable collectivity that is perceived to exist, irrespective of formal recognition, as a matter of historical fact. But while innate cosmopolitanism operates according to a top-down model of collectivity, it nonetheless recognizes and incorporates smaller units of collectivity. As such, it holds especial relevance at a time when international legal doctrine looks beyond the preeminence of states, but continues to be bound to them in practice. Following innate cosmopolitanism, the international system incorporates all members equally when it takes into account the different material position of each member vis-à-vis the collective whole. The rights and responsibilities enjoyed by each, and their political situation within the community, will vary accordingly. This article will explore the innate cosmopolitan contribution to international law by reference to two current discourses, concerning ethical legitimacy and constitutional theory, as they grapple with justifications for and the doctrinal viability of an expanding public order globally. Additionally, examples drawn from the activation of the crime of aggression in the Rome Statute, and the Kadi case, will be considered for the critical light they throw on innate cosmopolitan theory.

The authors participated in the ICC Review Conference held in Kampala in June 2010, which adopted by consensus a package agreement on the crime of aggression. This contribution presents some impressions from these negotiations. It was rather unexpected that consensus agreement could be reached, and the authors offer some explanations why this was possible. They also analyse the key elements of the agreement. After the international criminalization of aggression has been debated for decades, a decisive step has now been taken towards bringing this crime within the effective jurisdiction of the International Criminal Court.

The essay argues that the absence of an international treaty definition of aggression in international law should not preclude the prosecution of its perpetrators. Two legal regimes of responsibility, namely the prohibition against aggression as an international wrongful act and the crime of aggression have been entangled. Once one separates the criminal liability of individuals from state responsibility, a definition of the crime of aggression can be seen. According to the author, the contours of such a new definition contain the requisite degree of certainty for judicial approaches instead of merely political approaches. Consideration is also given as to whether conspiracy to wage a war of aggression may also be regarded as a separate crime within international criminal law.

A few years before the expected convening of the First Review Conference on the Statute of the International Criminal Court, the Special Working Group for the Crime of Aggression has made very significant progress in preparing the ground for enabling the Court to exercise its jurisdiction over what the Nuremberg Tribunal famously called the ‘supreme international crime’. The complex structure of this absolute leadership crime has been fully explored, including its implications for the interplay between the definition of the crime and the general principles of international criminal law. At the same time, the crucial analytical distinctions between state and individual conduct as well as between the substantive elements of the crime and the possible procedural role of the UN Security Council appear to be generally accepted. In the light of the momentum achieved on the diplomatic level, the First Review Conference presents a distinct and historic window of opportunity to the world's political leadership to complete the Rome Statute and thereby prevent its prominent lacuna from becoming permanent and thus turning into a legitimacy gap. The final phase of the negotiations should be guided by two principles. First, the substantive definition of the state act of aggression should stay within the legitimate limits of international criminal justice by not exceeding undisputed general customary international law. Second, a possible procedural role for the Security Council must not have the practical effect of placing the permanent members of the Security Council beyond the reach of the law.

This contribution is dedicated to Professor John Dugard. It discusses the most difficult issue to be resolved in the negotiations on the crime of aggression: the role of the Security Council in the exercise of jurisdiction over this crime by the International Criminal Court. The International Law Commission suggested a solution in the 1990s, but failing the required support and in the absence of subsequent agreement the 1998 Rome Conference could only prospectively give the Court jurisdiction over the crime of aggression. The post-Rome negotiations are characterized by, on the one hand, support from the five permanent members of the Security Council for the thesis that it should be exclusively for the Security Council to determine whether or not an act of aggression has been committed (as a precondition for the exercise of jurisdiction by the ICC) and, on the other hand, a rejection of this thesis combined with a search for alternatives by many other states. According to the analysis below, in relation to cases involving the crime of aggression the preferred way for the ICC to proceed is to exercise jurisdiction over this crime after a determination of state aggression has been made by the Security Council. Nevertheless, the view according to which such a determination could exclusively be made by the Council is rejected, on the basis of the rules of the Charter, the practice of the Security Council and the General Assembly, and decisions of the International Court of Justice. Finally, an alternative arrangement is suggested for the cases in which the Security Council is prevented from acting because of the use of the veto or because of lack of support from its members.