International Law

International law governs relations among states and other international actors — treaties, customary law, the use of force, and international institutions.

Scope

It covers the sources of international law, statehood and sovereignty, treaties, the law of war and peace, and international organizations and adjudication.

Core questions

• What are the sources of international law?
• How is international law made and enforced without a world government?
• When may states use force?
• How binding is international law?

Key concepts

• Sources of international law
• Sovereignty
• Treaties and custom
• Use of force
• International institutions
• Compliance

Key theories

The law of nations

Grotius systematized the law of war and peace, founding modern international law on natural law and the practice of states.

Compliance with international law

Henkin argued that 'almost all nations observe almost all principles of international law almost all of the time'.

History

From Grotius's founding synthesis, international law developed through positivist state-consent theories, the post-1945 UN order, and human-rights and institutional expansion, amid ongoing debate about its enforceability.

Debates

Is international law really law?

Whether rules without centralized enforcement count as law and how they bind states.

Key figures

• Hugo Grotius
• Louis Henkin

Seminal works

• grotius-1625
• henkin-1979

Frequently asked questions

How is international law enforced?

Largely through state consent, reciprocity, reputation, and institutions rather than a central enforcer — yet compliance is generally high.