Customary international law refers to obligations that arise from established state practice rather than from formal written agreements, such as treaties. Customary law on state responsibility for wrongful acts, including the expropriation of private property, is highly relevant to the study of international investment law.
Articles on Responsibility of States for Internationally Wrongful Acts (with Commentaries).
These articles, which codified the customary law on state responsibility, were adopted by the International Law Commission of the United Nations in 2001 after more than four decades of discussion. Visit the UN's Audiovisual Library of International Law to access the procedural history of the International Law Commission's codification of the law of state responsibility, as well as links to related documentation. For additional analysis and commentary on this codification, consult the reference books described below.