This chapter briefly discusses the nature of the international legal system. The premise is that the structure of the international legal system is fundamentally different from that of national legal order: contrary to the vertical structure encountered in domestic settings, in international law the structure is horizontal. States enjoy sovereign equality, while both international law-making and international adjudication are based on the consent of the States. There are various theories that have attempted to describe the nature of the international law, including naturalism, positivism, formalism, and realism. Also significant is the the existence of a certain hierarchy in the international legal system, in the sense that there are some peremptory norms of international law, such as the prohibition of torture and genocide, to which there is no derogation.
