Michael Mattler

Michael Mattler was the Assistant Legal Adviser for Treaty Affairs at the U.S. Department of State from 2014 to 2025, serving the principal legal adviser to the Department of State and other executive branch agencies on U.S. and international law and practice related to the negotiation, conclusion, implementation, and interpretation of treaties and other international agreements. From 2008 to 2012, he served as Chief Counsel to the U.S. Senate Committee on Foreign Relations’ Minority Staff under Ranking Member Richard Lugar.

Earlier in his career, he served as an Attorney-Adviser in the U.S. Department of State’s Office of the Legal Adviser, where he advised on issues including U.S. participation in the United Nations and other international organizations, international claims and investment disputes, bilateral relations with countries in the Near East and South Asia, and the law of armed conflict, and represented the United States before the International Court of Justice.

He is a member of the American Law Institute, where he serves as an Adviser to the Institute’s Restatement (Fourth) of the Foreign Relations Law of the United States. He is also a member of the American Society of International Law, and a past member of the Society’s Executive Council.