By way of conclusion, this chapter seeks to provide an overall assessment of what draws the Court and the Commission together, and of the impact that their “special relationship” has produced. In pulling the threads together, it explains that the interaction between the two organs has turned out differently to that which was originally envisaged, and that the great weight accorded by each of them to the work of the other has challenged the exclusive basis of State consent for international law’s validity. In a legal system that remains heavily dependent on unwritten rules of customary international law that require authoritative determination, the ultimate result has been that the Court and the Commission together assume a public order role not foreseen for either of them by their founders.

This chapter provides a detailed account of the impact that the Commission’s work has had in shaping the Court’s case-law. In addition to surveying and classifying all those instances in which the Court has to date been ready to refer expressly to the Commission’s output, the chapter demonstrates that reliance on the Commission’s work has often been more implicit. The question is then posed as to the basis for such recourse and the advantage afforded by it.

This chapter sets the scene for an appreciation of the contemporary relationship between the Court and the Commission by tracing its roots in the broader ideal of the pacific settlement of disputes and the rule of law in international affairs. Taking stock of developments dating back to the nineteenth century, it illustrates that the long-standing movements for an international court and for an international code were not unrelated, and that a certain vision did exist for the way in which their present institutional manifestations were to interact. That original vision, which has been lost in time, has thus far attracted less attention from commentators than its importance requires.

This introductory chapter explains the scope and purpose of the present study; the methodology pursued; and the structure of argument presented in subsequent chapters.

This chapter addresses in detail those rare occasions in which the Court and the Commission have adopted differing positions on the legal questions before them. In exploring both the potential for such disagreements and how they have been handled, the chapter shows that these instances attest to the strength of the inter-institutional relationship rather than undermine it. It also points out, however, that harmony comes at a cost.

This chapter addresses the relationship between the Court and the Commission beyond the printed page. By focusing attention on the movement of members from one institution to the other, and to the customary exchanges in Geneva between the members of both the UN organs, it reveals the extent and contribution of the more subtle ties that bind the Court and the Commission.

This chapter examines the unparalleled influence that the Court’s decisions have had on the Commission’s codification and progressive development of areas of the law under its consideration. It illustrates not only the great extent to which many of the Commission’s propositions have borrowed their authority from the pronouncements of the Court, but also the significant impact of the latter on the Commission’s choices concerning terminology and programme of work. The chapter further demonstrates the Commission’s conscious efforts to support the Court’s cause more broadly, including by encouraging the expansion of the Court’s jurisdiction and by promoting the doctrine of the sources of international law enshrined in its Statute.

Building on Derrida’s celebrated analysis of the term ‘supplement’, this chapter investigates the fundamental ambivalence of supplementary means of treaty interpretation. While the general philosophy of the Vienna Convention interpretive regime rests on the assumption of a hierarchy between the primary means set forth in Article 31 of the Vienna Convention and the supplementary means of Article 32, qualifying certain means as supplementary presumes that the primary interpretive means are somewhat lacking and in need of a complement. The chapter also focuses on the ‘danger’ of such supplement that has been highlighted in practice, namely, that supplementary means themselves need to be interpreted before they can be used in an interpretive inquiry, reinforcing the larger point made in the book that it is impossible to get an unmediated access to any signified. The chapter argues that since supplementary means are not comprehensively listed in the treaty interpretation regime, a virtually endless number of materials can be made relevant in treaty interpretation discourse through the channel of supplementary means.

How does one ascertain the object and purpose of a treaty? Can a treaty have more than one object and purpose? What does giving effect to the object and purpose of a treaty mean in practice? Despite such fundamental uncertainties surrounding them, the ‘object and purpose’ are widely resorted to in the practice of treaty interpretation. This chapter argues that the object and purpose doctrine is coextensive with a large amount of interpretive discretion. The identification of the object and purpose of a treaty a largely indeterminate process, and the assumption that the treaty makers necessarily want the object and purpose of their treaty to be implemented under all circumstances leaves the treaty interpreter with considerable normative power that can hardly be resisted given the very terms of the assumption. The chapter argues that consideration of the finality of a treaty cannot be an exercise in abstract logic, but meet the requirements of practical reason.

In this chapter, Massimo Lando focuses on the advisory jurisdiction of international courts and tribunals. This chapter explains that, traditionally, advisory opinions are not seen as a means of inter-State dispute settlement. However, it argues that recent developments justify re-assessing this traditional view. This chapter claims that the most significant development in this context is the judgment on preliminary objections delivered by the Special Chamber of the International Tribunal for the Law of the Sea in the maritime dispute between Mauritius and Maldives, which gave binding effect to the determinations made by the International Court of Justice in its 2019 advisory opinion concerning the decolonisation of Chagos. This chapter evaluates the Special Chamber’s decision by considering its impact on the Eastern Carelia doctrine and the Monetary Gold principle, as well as its implications for the legal effects of advisory opinions and for the legitimacy of exercising the advisory function.

In this chapter, Daniel Franchini and Russell Buchan examine the status, nature, content, and scope of the obligation of peaceful dispute settlement. This chapter traces the emergence of this obligation under customary and conventional international law, analyses the conditions that trigger its engagement, and explores what measures disputants must take in order to discharge this obligation. This chapter maintains that the peaceful settlement obligation is an interstitial norm insofar as it influences the interpretation and application of other rules of international law relevant to the peaceful settlement of disputes.

In this chapter, Sir Michael Wood examines the future of the international dispute settlement system. The core claim of this chapter is that continuity is, and will continue to be, this system’s defining feature. It observes that the fundamentals of inter-State disputes have changed little since 1920. Most notably, consent to third-party dispute settlement remains at the heart of the system, as does a widespread reluctance by sovereign States to give that consent in advance of disputes arising. The Optional Clause, for example, remains unchanged after 100 years, as does States’ unwillingness to accept it or to do so without extensive reservations. That said, and reflecting on the chapters contained in this collection, this chapter accepts that there have been new and important developments in the international dispute settlement system in recent years and, providing their promise is realised, they will perform a critical function in maintaining international peace and security.

In this chapter, Sir Malcolm Evans examines the role and legitimacy of international human rights mechanisms of dispute settlement. This chapter argues that the relationship between international dispute settlement and the work of the United Nations human rights treaty bodies is demonstrated by a series of cases brought by Qatar against the United Arab Emirates before both the International Court of Justice (ICJ) and the UN Committee on the Elimination of Racial Discrimination (CERD). This chapter explores some of the tensions which have been revealed concerning the interplay between the work of the CERD Committee and that of the ICJ and how each responded to them. It notes that the multifaceted and sui generis nature of their work means that they do not operate in a single ‘conceptual space’ and that the nature of the treaty bodies, their role and function, and the environment in which they work need to be borne in mind if their work is to be properly appreciated, understood, and engaged with.

This chapter discusses how international courts operate, and how their jurisdiction is dependent on consent of states. It goes systematically through notions of jurisdiction, admissibility, interim measures, and compensation, ending with a discussion of advisory opinions and the possibilities for judicial review