Washington lawyer whose arguments before the Supreme Court led to a 1962 decision that gave federal courts the right to redraw state electoral districts to reflect population shifts. Charles Sylvanus Rhyne was born on a cotton farm near Charlotte, N.C., on June 23, 1912. He graduated from Duke University and studied at its law school, where he became a friend of a classmate, Mr. Nixon. Mr. Rhyne finished his law degree at George Washington University. He opened a law office in Washington in 1937 and built a practice specializing in municipal and aeronautical law. He published seven textbooks in these fields. In 1955 he was elected president of the Bar Association of the District of Columbia after promising to integrate the association by striking the word ''white'' from its constitution as a qualification for membership. From 1971 to 1973, he was President Richard M. Nixon's special ambassador to the United Nations high commissioner for refugees. During the Watergate scandals, he was the lawyer for Rose Mary Woods, the president's secretary, in the inquiry into a gap of more than 18 minutes in a tape recording of conversations in the Oval Office. His first wife, the former Sue M. Cotton, whom he married in 1932, died in 1974. He is survived by his second wife, the former Sarah P. Hendon; two children from his first marriage, Peggy Fuqua of Bethesda, Md., and William S. of McLean, Va.; and two daughters from his second marriage, Sarah Rhyne of Arlington, Va., and Elizabeth Rhyne of McLean, Va.