International law is the body of international obligations and principles that govern how nations behave toward each other. Its origins date back to ancient times. Around 2100 BCE, the city-states of Mesopotamia signed peace treaties. Later, polities from the eastern Mediterranean to East Asia began to negotiate and sign various international agreements.

International law has several branches, including the International Court of Justice, which settles disputes between nations and issues advisory opinions on international law. Another branch of international law is the Interpol network of police organizations, which works to solve international crime. In addition, the Security Council, a committee of the United Nations, determines whether a situation poses a threat to international security. International law also provides protection for victims of human rights abuses who seek asylum in safer countries.

International law applies primarily to states, rather than to individuals. It is based on the principle of consent, and it is not universally enforced. However, states may choose to violate international law, such as by breaching a treaty. This will lead to disapproval from other nations, which may take coercive action, which could range from diplomatic sanctions to war.

As a result of international law, numerous international organizations have created binding laws. For instance, the United Nations Security Council can issue resolutions that impose sanctions on a state if it violates international law. Other international tribunals may also issue opinions that bind states and non-parties. The opinions of these tribunals can also provide useful insights into the nature of international law.