This chapter reflects on the institutional strength of the Security Council. It emphasises the fact that the Security Council forms part of the greater organisation of the United Nations, composed of 193 states. While it is obvious that the Security Council is a forum of power politics, the Council is not only composed of the powerful and the permanent. This chapter submits that the less powerful states do not necessarily need always to play a secondary role – especially if they team up. The chapter is also guided by the idea that less powerful states, in particular, have an interest in the rule of law guiding international relations as a means of constraining raw power politics. The chapter thus presents an institutionalist perspective. At its core, this perspective is about checks and balances, as well as the ability to take the interests of ‘the others’ into account (i.e., those that do not have a permanent seat at the Security Council). The chapter applies this perspective to examine the exercise of distinct Security Council powers pertaining to the use of force, UN sanctions, and counter-terrorism legislation, as well as to possible new work terrains for the Security Council.

Commissions of inquiry are not among the protagonists within the jus ad bellum architecture. Nonetheless, historically, several international commissions have been established in different institutional settings specifically to inquire into situations involving the use of force. These include theDogger Bank Inquiry into Russian firing at a U.K. trawler, the Lytton Inquiry regarding Japanese military action in Manchuria in 1931, and the 1961 Red Crusader Inquiry into a naval incident involving the United Kingdom and Denmark. A few contemporary commissions have also addressed jus ad bellum questions, even if not all were explicitlymandated to do so. These contemporary inquiries include international commissions established by the U.N. Security Council, Secretary-General, and Human Rights Council (HRC); regional commissions and national commissions. The Human Rights Council in particular has been very active lately in establishing commissions of inquiry.Despite the identity of their parent body, the HRC commissions have generallymade reference to areas of law beyond human rights, particularly international humanitarian law and international criminal law.

Given their direct engagement with law, commissions of inquiry have loosely been characterized as a new form of adjudication offering some accountability prospects. As these commissions tend to operate in peace and security contexts, this Chapter assesses the current and potential role of commissions of inquiry in the overall legal framework regarding the use of force. The Chapter aims to locate commissions of inquiry within the greater jus ad bellum architecture. It portrays the diversity of the inquiry landscape and zeroes in on the Kosovo and Iraq Inquiries as concrete examples of inquiry practice operating in situations that evoked fundamental jus ad bellum questions. The Chapter also offers thoughts on the accountability potential of commissions of inquiry and on how they relate to other jus ad bellum actors.

Section II first presents the most relevant contemporary international, regional, and domestic commissions of inquiry and interrogates how they have construed a jus ad bellum dimension into their mandates. Given the Human Rights Council's activity in establishing commissions of inquiry, it is specifically examined whether, given the recent activation of the International Criminal Court's (ICC's) jurisdiction over the crime of aggression, future HRC commissions of inquiry may be expected to become more active in the jus ad bellum domain.

This chapter revisits customary international law (hereafter CIL) as a source of international criminal law (hereafter ICL) in the era of the International Criminal Court (hereafter ICC). Most contemporary reflections on the role of CIL in ICL and most observations regarding creative judicial identification processes still tend to zero in on the International Criminal Tribunal for the former Yugoslavia (hereafter ICTY). True, the 1990s were a decade-long experiment, or perhaps, indeed, an extended “Grotian Moment.” In any event, it was a period of accelerated, and at times artificial, CIL creation on a variety of ICL issues by the ad hoc tribunals. The ICTY's innovative methodologies nourished theories about the fragmentation of sources and ensuing claims regarding the existence of autonomized regimes. Being predominantly based on ICTY experiences, these claims may well have become outdated. The coming into operation of the ICC Statute has gradually engendered a new momentum that is best described as the “Codified Moment.” In this new ICC era, CIL plays a much less prominent role.

This chapter explores the decline of CIL in ICL. It begins by delimiting the concept of “international criminal law” and highlights some consequences of this delimitation for a discussion on the role of CIL. It argues that the essence of this area of law is its judicial application as part of a process to determine guilt of individuals and to impose a sentence. Hence, only judicial agents truly apply ICL, and they do so vis-a-vis individuals. By implication, ICL does not operate in a traditional interstate setting, a feature that also has consequences for CIL formation and identification.

The chapter then presents the causal claim that this decline is a direct consequence of the introduction of the ICC Statute and the move toward a universal and more consent-based regime. As will be demonstrated, the ICC Statute's design reflects the drafters’ explicit resolve to marginalize CIL. Subsequently, this chapter argues that the move away from CIL in ICL can itself be explained by the difficulties inherent in grounding rules of ICL in CIL. This normative claim is developed through an analysis of different types of rules, that is, procedural rules, substantive rules regarding the definition of crimes, and rules regarding modes of liability.