This chapter addresses the Court’s jurisdiction in contentious cases and its jurisdiction in advisory opinions, using specific examples from the Court’s judgments and opinions. It considers whether a novel approach is needed to confer on the Court compulsory jurisdiction across a wider range of disputes.

This chapter examines specific aspects of the Court’s procedure in contentious cases. The authors focus on the key features of procedure: the institution of proceedings; provisional measures; preliminary objections; intervention; and non-appearance. For each of these aspects of procedure, the authors set out the current rules and practice, commenting on the way in which they have evolved, and making some suggestions for further innovation by the Court. They note that there have been recent calls urging he Court to codify aspects of its practice on procedural issues into generally applicable rules. While this might seem an attractive approach, the authors argue that this has the potential to unduly restrict the way in which the Court addresses cases – each of which may have its own particular procedural needs. They emphasise the need for the Court not to be overly prescriptive, but to ensure that it retains power to ensure a fair and just outcome in each particular case.

The chapter considers the contribution of the ICJ to the law of the sea, highlighting four areas where the Court has made a key contribution to the development of the law: maritime delimitation cases, the status of islands and rocks, navigational rights in straits and lastly, the conservation of natural resources. The author notes that the Court’s influence is not equal in all of these areas, but emphasises the significant rule that the Court has played in developing the principles and rules of international law applicable to maritime boundary delimitations.

This chapter on fact-finding and expert evidence considers how the Court has treated competing evidentiary claims, and how it engages in a fact-finding process, looking at the evolution of the Court’s process in this regard. The author evaluates the significant criticism that has been directed against the Court in respect of its approach to fact-finding and the ways in which the Court has begun to address those criticisms.

The chapter examines the ICJ’s contribution to the law on the use of force. The author considers the Court’s case law on the prohibition of the use of force and its potential exceptions, most notably the law on individual and collective self-defence. He identifies the main conceptualisations, inconsistencies, disagreements, and limitations of the Court’s opinions, arguing that although the Court initially had a significant influence, it has faded significantly over the years as a result of what appears to be a conscious or strategic decision of its judges.

The chapter deals with the role of the ICJ in the development of international law from both a doctrinal and a practical perspective. It considers concrete examples of the way in which the Court’s judgments and opinions have had an influence on the development of international law, and it concludes that the Court has in practice had a significant impact on the development of international law, even though that goes beyond its core mandate.

The ICJ’s contribution to the law on jurisdictional immunities is elucidated by Professor Roger O’Keefe. He argues that, through its case law in this area, the ICJ has affirmed basic aspects of the international law of jurisdictional immunities, clarified a few more specific points, and variously crystallised, consolidated, and catalyzed the further development of important customary rules on controversial issues in relation to civil and criminal proceedings respectively. Through its work in this field, the Court has reasserted an orthodox, possibly conservative vision of the role of jurisdictional immunities in the international legal order.

This chapter describes the working practices of the Court, and the reforms made to increase the speed of cases, as well as to improve the processes. The author notes that the Court has demonstrated significant agility in its more recent amendments to the Rules to take account of the worldwide pandemic, and argues that there is evidence to suggest that the Court is becoming more assertive, moving away from its traditionally high level of deference to States.

The chapter considers the ICJ’s contribution to the law of State responsibility, looking back to the Court’s contribution to the codification of that law by the ILC: looking at the Court’s current attitude to the ILC’s Articles on State Responsibility; and looking to the future, addressing one of the main challenges facing the Court in this field, that of multilateral disputes. The author concludes that the Court has been an important player in this field of international law, and it has made a significant contribution to vesting the ILC Articles with the authority they have today. According to this chapter, the Court has an important role to play going forwards in the growth and development of community interest litigation for the enforcement of erga omnes obligations.

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.