III Custom as a Source of International Law

Subject(s):

Customary international law

This chapter considers the question of whether custom is a source of international law. It discusses the constituent elements of custom, changes in customary law, the relevance of ethical and similar principles to customary law, and the extent of application of a rule of customary international law. In treating custom as a source of legal rules, international law does not deviate from the pattern discernible in municipal legal systems. Historically, at the international level, once the authority of natural law, in the sense of what was given by God or imposed by the nature of an international society made up of independent princes, had weakened, it was natural to derive legal obligations from the legitimate expectations created in others by conduct. However, the precise nature and operation of the process have always presented obscurities.