He is a member of the Panel of Arbitrators at ICSID and served as Chair and Member of a number of international arbitral tribunals (ICC, ICSID and UNCITRAL). He was appointed as a Judge ad hoc by Malaysia for the International Tribunal for the Law of the Sea in the case "Malaysia v Singapore" (2003); he was a Member of the International Law of the Sea Annex VII Tribunal in the same case, as well as in "Guyana v Suriname" (2005–2007).