Each state enjoys full sovereignty over its territory and therefore has, in principle, full jurisdiction over events and persons within its territory. The term “jurisdiction” is often associated with the power of a court to hear a case, but judicial or adjudicative jurisdiction is just one of three manifestations of jurisdiction. The exercise of jurisdiction is also manifested in the authority of states to prescribe rules (legislative or prescriptive jurisdiction) and the power of states to enforce rules (enforcement jurisdiction). Although the power of states to exercise jurisdiction follows from the principle of sovereignty, this power is not unlimited. Each state has to respect the personality and sovereign equality of other states, and overstepping this boundary entails a violation of public international law. This limitation is most pertinent when a state exercises jurisdiction outside its own territory, for example when it enforces domestic legislation outside of its territory or when it extends the application of its domestic laws to people, property, or events outside its own territory. This chapter discusses the scope of the jurisdiction of states when states exercise enforcement, prescriptive, and adjudicative jurisdiction in relation to persons, property, and acts outside their own territory.

This chapter begins by explaining why international lawyers typically begin discussions about the sources of public international law by referencing Article 38 of the Statute of the International Court of Justice (ICJ). It then introduces treaties and custom, which are the two main sources of law in this field, before discussing other sources, namely general principles of law, decisions of international organizations, unilateral declarations, as well as judicial decisions and the teachings of international legal experts. The chapter ends with a discussion of non-binding instruments, which do not contain binding legal rules, but are nonetheless significant in the international legal field, as they contain norms that impact the behavior of states.

International law on immunities consists of a body of procedural rules that limit when a state may exercise jurisdiction within its territory. These procedural rules could prevent a domestic court from exercising jurisdiction in a case involving a foreign state, a foreign state official, or an international organization. These rules could also prevent a police officer from exercising jurisdiction by arresting and detaining a foreign diplomat or a minister of foreign affairs. 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.

IHL has historically been divided into two main branches, consisting of rules that regulate the “means and methods of warfare”and the rules that deal with the “protection of persons and projects.” The rules governing the means and methods of warfare are known as “Hague Law” due to the fact that the main treaties governing this field of law were, for a long time, the 1899 and 1907 Hague Conventions and the annexed Hague Regulations. The provisions dealing with the protection of persons and objects hors de combat (“out of combat”) are known as “Geneva Law,” as these rules can be found in the Four Geneva Conventions of 1949. The two Additional Protocols of 1997 cover both norms concerning the means and methods of warfare, and those protecting individuals. This chapter begins with the foundations and the history of IHL, before discussing the scope of application of IHL 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 IHL.

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 as well as 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, and, in addition, the Permanent Court of Arbitration has undergone a sort of renaissance. The focus of this chapter will be on the settlement of inter-state disputes, as opposed to disputes between states and non-state actors or between non-state actors.

This chapter explores international law relating to the protection of the environment, a relatively new field of international law that covers a broad range of concerns. The pollution of the oceans and the seas, the extinction of animal species, deforestation, and climate change: these are all concerns addressed by international environmental law. This chapter begins by providing a brief overview of the evolution of international environmental law and explains the principal characteristics of this field of international law. It further considers the interrelationship with the concept of sustainable development, which is central to modern approaches toward protecting the environment. It then explores two of the principal concerns addressed by international environmental law: first, the conservation of flora and fauna; and, second, the prevention of pollution and related environmental harm. Furthermore, the chapter discusses compliance and enforcement mechanisms. Lastly, because environmental protection measures often have implications for international trade, it briefly deals with the interrelationship between international environmental law and trade law.

This chapter introduces the jus ad bellum: the rules of law determining when states may resort to war or, more broadly, the use of armed force. These rules must be distinguished from the jus in bello: these are the rules of law that apply in armed conflict (known as international humanitarian law). 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-defense. Finally, the chapter examines whether new exceptions to the prohibition of the use of force are emerging -- in particular, humanitarian intervention and the responsibility to protect.

This chapter will first discuss the main subjects of international law and explain their principal features. Second, this chapter will zoom in on states, the traditional and principal actors in the international legal system. It will discuss the criteria for statehood under international law, the role that recognition plays in this respect, and explain how new states emerge. Finally, this chapter will turn to an analysis of the right to self-determination, a notion that plays an important role in the creation of states and is considered to be the most prominent right of one of the subjects of international law: peoples.

This chapter begins by explaining why international lawyers typically begin discussions about the sources of public international law by referencing Article 38 of the Statute of the International Court of Justice (ICJ). It then introduces treaties and custom, which are the two main sources of law in this field, before discussing other sources, namely general principles of law, decisions of international organizations, unilateral declarations, as well as judicial decisions and the teachings of international legal experts. The chapter ends with a discussion of non-binding instruments, which do not contain binding legal rules, but are nonetheless significant in the international legal field, as they contain norms that impact the behavior of states.

This chapter introduces the jus ad bellum: the rules of law determining when states may resort to war or, more broadly, the use of armed force. These rules must be distinguished from the jus in bello: these are the rules of law that apply in armed conflict (known as international humanitarian law). 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-defense. Finally, the chapter examines whether new exceptions to the prohibition of the use of force are emerging -- in particular, humanitarian intervention and the responsibility to protect.

This chapter focuses on the rules set out in the 1969 Vienna Convention on the Law of Treaties (VCLT). The chapter begins with the concept of a treaty, before discussing treatymaking, 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 criminal law is the branch of public international law under which individuals may be held criminally responsible for the offenses of genocide, crimes against humanity, war crimes, and the crime of aggression. International criminal law seeks to prevent impunity by holding accountable those individuals who are responsible for serious violations of international criminal law. This chapter begins with the history of international criminal law, starting with the aftermath of the First and Second World Wars, and ending with the creation of a spate of international criminal courts and tribunals in recent decades. The chapter then covers substantive aspects of international criminal law, namely the crime of genocide, crimes against humanity, war crimes, and the crime of aggression. Finally, the chapter covers key procedural aspects of international criminal law, including the jurisdiction of international courts and tribunals, the admissibility of cases, modes of liability, and immunities. The International Criminal Court (ICC) will form a focal point in this chapter.