Cadieux joined the Department of External Affairs in 1941, served as senior adviser to Canadian members of the
International Control Commission in
Vietnam in 1954, and became the legal advisor to the Department of External Affairs in 1956. A professor of international law at the
University of Ottawa, he was the first Canadian to sit on the
United Nations International Law Commission. From 1964 to 1970, he was Under-Secretary of State for External Affairs. Cadieux served on the negotiating committee to determine maritime boundaries with the United States. and head of the Canadian Mission to the European Communities from 1975. He was appointed to advise the
Royal Canadian Mounted Police (RCMP) in 1978. He also wrote several books on Canadian diplomacy. In 1969, he was made a Companion of the
Order of Canada. ==Family==