International law is the body of rules and principles that governs relations among sovereign states and between non-state actors such as individuals, corporations, and organizations. Its principal functions include the settlement of international disputes, the prevention and prosecution of crimes against humanity such as genocide and war crimes, the enforcement of human rights, and the protection of the environment.

The most prominent sources of international law are treaties, customary law, and laws created by international agreements or conventions. Customary law is derived from the practice of states adhering to a particular norm out of a sense of obligation (opinio juris). International agreements and conventions can create laws that are binding upon the parties. These laws can be enforced by the use of coercive measures, including sanctions or military force, which must first be approved by the UN Security Council.

A major problem in the field of international law is that there is no centralized system of law enforcement. This has made it difficult to deal with growing transnational threats such as terrorism and environmental degradation. It also has prevented the creation of an effective international court of justice.

While international law does not impose the authority to directly compel nations to obey its laws, it is able to exert normative pressure on nations by being invoked in domestic and regional legal fora and through the work of international courts or human rights groups. International norms can also become internalised by a state and acquire “a take-it-for-granted quality that makes compliance almost automatic” (Finnemore and Sikkink 1998, 904).