 In addition to being a prolific author, Maier has served as Counselor on International Law to the Legal Adviser at the U.S. Department of State, as a member of the U.S. Secretary of State's Advisory Committee on Private International Law, and as a consultant to the Office of the Secretary of the Army on the Panama Canal Treaty Negotiations.Additionally, he has testified before congressional committees on various issues, including emergency presidential controls on international economic transactions.In 1985 he was an expert witness for the U.S. Government in civil litigation resulting from the Mariel boatlift.