International Law is a complex body of legal rules, norms, and standards that governs the conduct and relations between sovereign states and other recognized international actors, such as international organizations and, increasingly, individuals. It is a concept and an evolving legal institution that operates largely through the consent of states, as there is no single, universally accepted authority to enforce it.
The term was coined by the English philosopher Jeremy Bentham (1748–1832) in his 1789 book, Introduction to the Principles of Morals and Legislation. The modern system of international law, however, is often traced to the 1648 Peace of Westphalia, which established the principle of state sovereignty and the need for rules to govern relations between independent nation-states. The problem it solved was the need for a predictable framework for diplomacy, war, and peace in a world of independent political units.
The mechanism of International Law is primarily based on its sources, which are authoritatively listed in Article 38(1) of the Statute of the International Court of Justice (ICJ). These primary sources are: (a) international conventions (treaties), (b) international custom (general state practice accepted as law), and (c) general principles of law recognized by nations. Treaties, such as the 1969 Vienna Convention on the Law of Treaties, are binding only on the states that sign and ratify them, and are governed by the principle of pacta sunt servanda (agreements must be kept).
International Law connects directly to major global institutions like the United Nations (UN), whose Charter is a foundational document for the international legal system, and the ICJ, which settles disputes between states. It also connects to specialized areas like International Humanitarian Law (governing armed conflict) and International Criminal Law, which is enforced against individuals by the International Criminal Court (ICC).
Recently, the foundations of International Law have been challenged by new armed conflicts and geopolitical shifts, leading to debates about its effectiveness, particularly regarding the ban on the use of force in Article 2(4) of the UN Charter. However, the core structure, including the sources in Article 38(1) of the ICJ Statute, remains the doctrinal starting point for international legal reasoning. A recent development is the BBNJ Agreement (on marine biological diversity), which entered into force on January 17, 2026, as an implementing agreement under the 1982 UN Convention on the Law of the Sea (UNCLOS).