An Introduction to Public International Law

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.