International law is the set of norms and practices that govern relations among nations. It is derived largely from international treaties, but also from custom and state practice, and from judicial decisions. Since there is no superior authority to enforce the rules, they have the status of law only because states recognize them as such and act accordingly. The system has significant value, providing certainty, predictability and a sense of shared purpose in international affairs. But it is not without its problems. States often find it difficult to deduce legal rules from social practices and subjective beliefs and, as a result, there is considerable variation in the content of international law. Even the preparation of a treaty text is often an intense and time-consuming process, requiring difficult compromises to be made by states with very different interests and concerns.

The major themes of international law are:

Promoting peace by outlawing war (the United Nations Charter, 1945). Providing nations with methods and institutions for settling disputes peacefully through agreements governing negotiation, mediation, conciliation and arbitration (such as the International Court of Justice, 1946). Establishing standards for ship operations in Arctic waters in order to prevent oil, sewage and liquid chemicals from spilling into the ocean environment (the Polar Code, 2015). Defending the rights of children against child abuse and exploitation by establishing conventions and multilateral treaties that make the exploitation a criminal offense (Convention on the Rights of the Child, 1989). The articles that follow illustrate some of the many ways that international law takes shape.