This chapter focuses on the rules set out in the 1969 Vienna Convention on the Law of Treaties (VCLT). This chapter begins with the concept of a treaty, before discussing treaty-making, with a particular focus on the conclusion of treaties, their entry into force, and reservations to treaties. The chapter then delves into how treaties operate, namely their scope of application and their interpretation. Finally, this chapter looks at the invalidity, suspension, and termination of treaties.

International law on immunities consists of a body of procedural rules that limit when a state may exercise jurisdiction within its territory. International law bars the exercise of jurisdiction in such situations either because the exercise of jurisdiction would threaten the equality of sovereign states or because the capacity of the individual or organization to carry out their functions would be compromised. This chapter begins with the law on state immunity, which has evolved over the centuries from an absolute doctrine to a more restrictive one, which permits exceptions, in particular when states engage in commercial activities. The chapter introduces the immunities that apply to all individuals who serve as state officials, whether they serve as relatively low-level civil servants or as the president or prime minister. The chapter also deals with two special regimes, one governing diplomatic and consular agents who serve abroad, and the other governing international organizations.

Treaties are international agreements that create legal obligations for states, as well as other actors like international organizations. The number of treaties in the field of public international law has grown exponentially since the end of the Second World War, when states turned increasingly to international law and international institutions in order to ensure peaceful coexistence and cooperation. Certain branches of the field, such as international environmental law and international investment law, are now dominated by a substantial collection of treaties, while customary international law plays a secondary role. The importance of treaties in many branches of public international law heightens the importance of understanding ‘the law of treaties’, meaning the law governing this source of international law.

After a sketch of the history of the law of the sea and the traditional freedoms of the sea, this chapter discusses the various efforts to codify the law of the sea during the twentieth century, which culminated in the adoption of UNCLOS in 1982. Subsequently, the chapter examines the legal regimes governing the various maritime zones, as well as two international areas, the high seas and the Area. The chapter then takes up thematic issues in the law of the sea, namely the delimitation of maritime boundaries, the protection of the marine environment, the special interests of developing countries, and the system for the settlement of law of the sea disputes. The chapter concludes by noting that despite the relatively comprehensive scope of UNCLOS, a number of new challenges have arisen with respect to the law of the sea, especially as a result of human-driven climate change.

This chapter starts by briefly sketching the development of international human rights law. It then presents the main categories, or generations, of human rights and discusses their key characteristics. The chapter subsequently turns to several matters concerning the scope of human rights norms, including their addressees, their territorial scope of application, and the circumstances under which human rights may be restricted by the state. Finally the chapter explains the monitoring and compliance mechanisms for international human rights under the United Nations and the three major regional human rights systems.

This chapter begins by elaborating on the concept of a dispute, before providing a historical perspective on the evolution of the requirement to settle disputes peacefully. The chapter then explores diplomatic and legal methods of dispute settlement. Diplomatic forms of dispute settlement (also known as political or non-legal forms of dispute settlement) include negotiation, mediation, inquiry, and conciliation. Legal forms of dispute settlement include arbitration and adjudication. Resort by states to dispute settlement procedures, and in particular legal methods of dispute settlement, has grown exponentially in the last decades. Since the 1990s, the International Court of Justice has had an increasingly active docket of cases; in addition, the Permanent Court of Arbitration has undergone a sort of renaissance. The focus of this chapter is on the settlement of inter-state disputes, as opposed to disputes between states and non-state actors or between non-state actors.

International economic law is a field of public international law that regulates cross-border transactions in goods, services, and capital, as well as monetary relations between states. This chapter focuses on the branches of international economic law that govern international trade, international investment, and international monetary law. This chapter sets out the historical background, fundamental rules, and dispute settlement systems in the areas of international trade law and international investment law, and it concludes by introducing international monetary law. International trade and international investment law share some fundamental principles, such as non-discrimination, although most favoured nation treatment and national treatment take somewhat different forms in the two bodies of law. This chapter covers the Bretton Woods institutions, namely the World Bank and the International Monetary Fund (IMF), as well as the World Trade Organization (WTO).

This chapter introduces the three different manifestations of jurisdiction: enforcement jurisdiction, prescriptive jurisdiction, and adjudicative jurisdiction. The chapter focuses on the extent to which states may exercise jurisdiction in relation to persons, property, and acts that are outside of (or partially outside of) their own territory. With respect to prescriptive jurisdiction, the chapter introduces five different principles that are used to justify the extra-territorial application of legislation: the territoriality principle, the nationality principle, the personality principle, the protective principle, and the universality principle.

This chapter begins with the foundations and the history of international humanitarian law before discussing the scope of its application and the law governing the conduct of hostilities, namely the means and methods of warfare. The final sections discuss the law governing the protection of persons during armed conflict and the implementation and enforcement of international humanitarian law. In introducing international humanitarian law, this chapter focuses on the four Geneva Conventions of 1949 and the Additional Protocols of 1977.

This chapter introduces jus ad bellum: the rules of law determining when states may resort to war or, more broadly, the use of armed force. In order to put the current jus ad bellum rules into perspective, the chapter begins by introducing the concept of collective security and demonstrating how this was applied during the League of Nations era. The following sections set out the relevant rules of the UN Charter on the prevention and regulation of recourse to the use of force, with a particular focus on the prohibition on the threat or use of force. The chapter also discusses the collective use of force, meaning the use of force authorized by the Security Council, and the unilateral use of force in self-defence. Finally, the chapter examines whether new exceptions to the prohibition of the use of force are emerging, in particular humanitarian interventions and the responsibility to protect.