The chapter considers the process of nomination and election of judges, as well as their qualifications and the outcomes of the election process. It then examines the way in which the Court engages as a judicial body with the parties, with specific reference to the Court’s exercise of its advisory jurisdiction. Finally, it discusses the process of decision making, before drawing conclusions on the outcomes of that process, i.e. the judgments and opinions of the Court.

The chapter traces the origins of the ICJ in its predecessor, the PCIJ, and then considers the Court’s core functions: deciding the disputes submitted to it and exercising its advisory functions. It also critically examines the Court’s functions in finding and developing the law, and in maintaining international peace and security.

This chapter considers the ICJ’s relationship with other courts and tribunals through the dual prism of integration and fragmentation. The author argues that three factors influence the degree of the Court’s integration or fragmentation: the identity of the court, the substance of the law, and the procedures employed. The author selects three legal issues that have been considered by the ICJ and other courts and tribunals in recent years: jurisdiction over issues of immunity involving treaties that do not expressly refer to immunity; inferring specific intent for genocide; and the nature of consular assistance as a treaty obligation, individual right or human right. These issues provide insight into the way that identity, area of law and procedure influence integration or fragmentation among international courts.

This chapter examines the ICJ’s influence on international environmental law. Drawing on concrete examples, the author identifies six ways in which the Court’s jurisprudence has contributed to environmental law: by articulating foundational principles; by acting as a gatekeeper for customary international law; by elaborating existing principles; by interpreting environmental agreements; by valuing environmental harms; and by incorporating environmental considerations into other areas of international law. The author reflects on potential future evolutions of the Court’s role in the international environmental law space, given the increasing number of disputes that the Court has addressed in this field in recent years.

The chapter assesses the effectiveness of the ICJ. The authors set out an evaluative framework for assessing the Court’s effectiveness, adopting a goals-based analysis. They identify the ICJ’s goals, and then consider the structural features of the Court that assist and hinder it from achieving those goals. By reference to specific examples, the authors then consider whether the ICJ has achieved its goals in practice, concluding that its record of achievement produces mixed results, but highlighting the Court’s success in preserving confidence in international adjudication.

This chapter explains the Court’s significant role as the ‘master of the sources’ of international law. The author considers what he defines as the ‘repressive dimension of Article 38’, before turning to consider the ways in which the Court has concretely used its role in respect of the sources of international law. Finally, the chapter critically examines how repression and mastery can often work together in international legal thought.

The International Court of Justice held its first sitting on 18 April 1946 and heard its first two cases in 1948: it heard preliminary objections in The Corfu Channel Case from late February to early March, and it held hearings in the advisory opinion on Conditions of Admission of a State to Membership in the United Nations (Article 4 of the Charter) in late April. Those first two cases were emblematic of the kinds of disputes that the Court would eventually hear and resolve as part of its ordinary caseload: they both dealt with practical issues, with significant political implications, and were an opportunity for the Court to provide guidance to the broader international community on disputed issues of international law. They provided the Court with scope to fulfil its mandate as the principal judicial organ of the United Nations; to function as a prominent interpreter of international law, as it is used and applied in practice. As international law has become more present in global policy-making and in academic and journalistic commentary, the International Court has come to occupy an essential and increasingly visible role in international relations, and has exercised jurisdiction over a significant number of international disputes addressing the same matters as are being wrestled with in the halls of the United Nations, and in ministries of foreign affairs across the world, and are being discussed as leading stories in international newspapers.

The second part concludes with a chapter on effective advocacy before the ICJ, by Samuel Wordsworth QC and Kate Parlett. It examines both written and oral advocacy before the Court, with the fundamental objective of the advocate in all cases being to persuade, making it essential to consider what will be of most utility to the judges when they come to reach a decision on the case. They also emphasise the significant role the advocate has to play in the pre-litigation stage and in early procedural exchanges: she or he must bear in mind that they have a dual function of presenting the best case for the client to the Court, while also persuading the client as to the most effective way in which to do that.

This chapter assesses the contribution of the ICJ to the law of international organisations. It emphasises the limited role of the Court in this field, setting out the multiple reasons for this: parts of the law were developed before the Court commenced its work; and the Court has only had intermittent opportunities to consider it through its cases. The author argues that the Court’s approach reflects a more general ambivalence of classic international law when it comes to international institutions: that it emphasises the centrality of States in the international legal system, notwithstanding the steps that have been taken by States to institutionalise significant areas of international law.

This chapter examines the law of treaties in the jurisprudence of the ICJ. The author highlights the Court’s position on key selected issues of interpretation: specifically the language of the treaty; time and treaty interpretation; and the role of policy. The chapter also considers issues of systemic integration, hierarchy and concurrence of rules.

The chapter provides a thorough analysis of the Court’s jurisdiction to order provisional measures and its procedure. The author identifies an evolution in the Court’s practice on provisional measures, with the Court most recently developing specific conditions for the indication of provisional measures. The author examines those conditions and their elaboration through the Court’s caselaw, together with the Court’s findings as to the binding effect of its provisional measures orders.