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.

This chapter frames the interpretive regime of modern international law as a historical contingency and aims to trace its genealogy through an analysis of the codification process that led to the current regime. The contingency of the rules of treaty interpretation is hardly recognized in the official discourse. Treated as a matter of common sense or trans-historical customary international law, the rules of treaty interpretation set forth in the Vienna Convention on the Law of Treaties have for instance been applied to the interpretation of treaties dating back to the nineteenth century and a whole range of treaties concluded in the twentieth century before the entry into force of the Vienna Convention. There is, however, ample evidence that the interpretive approach of the Vienna Convention has by no means prevailed throughout the history of international law. This chapter identifies a series of factors ranging from the intellectual history of the discipline of international law and the contingencies of the codification process, to the political circumstances of the Cold War era and the rise of permanent international tribunals that can account for the normative outcome of the Vienna Convention regime.

The doctrine of attribution in international law has been defined, in large part, by the International Law Commission’s (ILC) provisions on attribution of conduct in the Articles on State Responsibility for Internationally Wrongful Acts (ARSIWA). It is uncontroversial to note that despite the influence of the ILC’s rules on attribution, the regime of international responsibility remains underdeveloped. In addition to being underinclusive, the rules of attribution in ARSIWA are beginning to appear outdated. The central question, therefore, is whether the rules of attribution in ARSIWA are flexible enough to accommodate two disparate trends. On the one hand, we have witnessed an outsourcing of public functions to private actors in areas such as immigration, prison management, and education, whereby privatization has reduced state control and, consequently, potential state responsibility. On the other hand, there is a marked centralization of power in SOEs, some of which are now playing a global role as investors. This chapter assesses whether the default rules on attribution are flexible enough to manage both ends of the spectrum of state activity, which will be a crucial issue for regulators going forward.

The author starts by observing that discussions about the foundations and the limits of the powers of international courts, including those of the European Court of Human Rights (hereafter ECtHR), turn around the aims of achieving legal certainty, ensuring legitimacy and justice, and avoiding conflicting obligations which may emanate from different regimes of international law. The chapter reflects on these aims from the perspective of consent as the common basis of the main sources of international law, as listed in Article 38 of the Statute of the International Court of Justice. Proceeding from the case law of the ECtHR, the chapter explores how the recent work of the International Law Commission conceives the role of consent in respect of the main sources of international law, and whether the jurisprudence of the ECtHR remains within the framework of general international law so enunciated.

The starting point for discussion and analysis of the sources of international law is almost invariably art 38 of the Statute of the International Court of Justice (‘ICJ Statute’), the International Court of Justice being the primary judicial organ of the United Nations. Article 38 lists the sources of international law as comprising treaties, custom, general principles of law, and – as subsidiary means for determining the law – judicial decisions and academic writing. However, in the 75 years since the adoption of the ICJ Statute, newer sources of legal obligation have emerged for the international community. These often involve non-state and intergovernmental actors in their creation. This chapter explores both the traditional and newer sources of international law and assesses how they are adopted and created.

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.

International organisations include global organisations such as the United Nations and regional organisations such as the European Union. The chapter examines constituent instruments and their interpretation, membership (which may include non-state entities) and withdrawal, including the withdrawal of the United Kingdom from the European Union. International organisations have the capacity to enter into treaties but may only conclude agreements in those areas in which they are competent to act. The Vienna Convention of 1986 adapts the rules of the 1969 Convention to apply to international organisations, but it is not yet in force. The chapter examines bodies which play a role in recommending or negotiating treaty texts (including the United Nations, UN Sixth Committee and the International Law Commission) and those which play a role in settling disputes (such as the International Court of Justice) and in monitoring compliance (such as the Human Rights Committee). It looks at special cases, including the OSCE, Commonwealth and European Union.