Associate lawyer (9/18/61-6/30/69), partner (7/1/69-10/31/69; 9/15/73-1/16/84; 4/1/88-12/31/00) and special counsel (1/1/01-2/28/05) White & Case LLP (New York City and Washington, DC).
Assistant Legal Adviser for European Affairs (11/1/69-6/30/71), Deputy Legal Adviser (7/1/71-12/31/72) and Acting Legal Adviser (1/1/73-8/31/73) in the Office of The Legal Adviser of the United States Department of State.
Judge, Iran-United States Claims Tribunal (1/16/84-present).
Deputy Special Counsellor to the President of the United States (1/1/87-4/30/87)(rank of Deputy Assistant to the President, sub-Cabinet level of Deputy Secretary of a Department)(on leave from the Iran-United States Claims Tribunal).
Judge ad hoc, International Court of Justice (2014-present)(in three contentious cases, one by appointment of the Republic of Colombia, two by appointment of the United States).
Arbitrator Member, Twenty Essex Chambers (1/1/01-present).