International law is the body of rules that regulates relations between states and, to a lesser extent, between states and non-state actors (including international organisations and some individuals). It establishes normative guidelines, methods and a common conceptual framework for all of the world’s actors — primarily sovereign states but also corporations, NGOs, international tribunals and other institutions. It covers a wide variety of issues and topics, including peace and conflict settlement, economic and trade matters, international crime and the treatment of refugees, environmental problems and terrorism.

It is not just a set of binding rules, but also reflects an evolving body of principles and values that guide behaviour between States and amongst their citizens. It incorporates a rich mix of customary and conventional law, as well as laws made through international agreements, including the over 560 major multilateral treaties deposited with the United Nations. It also includes a series of universally recognised values and standards that have developed through popular movements backed by the United Nations or endorsed by states as the basis for their law.

Modern international law dates back to the turn of the twentieth century when states gathered in The Hague to establish their first laws of war, arms control and the League of Nations in the hope of ushering in an era of peace and prosperity. However, the calamitous events of two colossal world wars dealt a devastating blow to that idealistic belief, although they did set in motion a rapid expansion of international law, especially in the areas of civil rights, refugee law and admiralty and maritime law.