The rapid development of international law post-World War II also coincided with greater reliance upon treaties as a source of international law. Treaties had always been recognised as a source of international law, and their status was confirmed in art 38 of the ICJ Statute. It was the development of the UN, with its emphasis upon international law and focus upon treaty-making as a means of not only peaceful resolution of disputes but also multilateral agreement between States on matters of common concern, that was the catalyst for a greater reliance upon treaties in the conduct of international relations. This chapter begins by examining the growth of treaty-making, before considering what a treaty is, including the nature of 'instruments of less than treaty status'. It then covers treaty negotiation, creation and entry into force; reservations, objections and declarations to treaties; and legal obligations arising once a treaty has entered into force. The chapter then turns to treaty interpretation, and then examines how treaties are voided or ended through invalidity, suspension or termination. The chapter concludes with a discussion of amendment and modification of treaties.

Law-making is not a straightforward process in international law. This chapter focuses on the various law-making processes and structures available for creating international law. It first considers the traditional sources of international law as set out in art 38(1) of the Statute of the International Court of Justice generally and the concept of hierarchy of norms and relative norms before considering each of the art 38(1) sources in turn. The chapter concludes by considering alternative sources of international law not covered by art 38(1): 'soft law' including that created by non-State actors, and the role of the UN in creating international law.

Human rights are commonly invoked by States and individuals alike. Most recently there has been a spate of cases with a State accusing another of acts of genocide. The Convention on the Prevention and Punishment of the Crime of Genocide (Genocide Convention) is the first human rights treaty which the General Assembly of the United Nations adopted in 1948. As an example, it gave South Africa the basis for accusing Israel of acts of genocide for their activities against Palestinians living in Gaza even though it had no immediate and direct interest in the situation. Since the Genocide Convention a host of other treaties have been adopted and ratified by States and the United Nations machinery for administering them is now complex and sophisticated, despite the traditional enforcement mechanisms that domestic lawyers are accustomed to having behind them.

This chapter considers how resort to the use of force is addressed in the UN Charter, with particular reference to self-defence, including collective self-defence, and anticipatory self-defence. The contemporary right of self-defence is also assessed in light of the rise and influence of non-State actors. United Nations-sanctioned use of force is considered, with particular reference to the mechanisms that exist in Chapter VII of the UN Charter. The use of force by invitation, humanitarian intervention and the 'responsibility to protect' are also considered.

Jurisdiction refers to the ability of a State to make and enforce its laws. While often related to sovereignty, and intrinsically linked to its territory, jurisdiction can exist without a connection to territory. Jurisdiction can be held to exist in a variety of contexts, depending on the location of events, the nationality of participants or the surrounding circumstances, and will also indicate whether a State may be able to undertake enforcement action to uphold its law. This chapter considers the nature of jurisdiction insofar as it affects persons, corporations, ships and aircraft. The different types of recognised international law jurisdiction are each assessed, including territorial jurisdiction, nationality jurisdiction, universal jurisdiction, the protective principle, and passive personality jurisdiction. Jurisdictional immunities as they apply to States, Heads of States, State officials and diplomats are also considered.