Robert B. Stewart, 71, dean emeritus of the Fletcher School of Law and Diplomacy at Tufts University, died of cancer June 8 at the Lutheran Medical Center in Wheat Ridge, Colo., a suburb of Denver. He was a resident of East Orleans, Mass., and was visiting a son at the time of his death.

Dean Stewart was a State Department official working on British and British Commonwealth affairs from 1938 to 1945. He also attended the San Francisco Conference on the United Nations in 1945.

He then went to Fletcher as its dean. He held that post until 1964, when he became a professor on the Fletcher faculty. He was named a dean emeritus upon his retirement in 1975.

Dean Stewart was a member of the Foreign Service Selection Board in 1950 and a member of the State Department's executive reserve from 1957 to 1961.

A native of Matewan, W.Va., he earned bachelor's and master's degrees at the University of Kentucky. He was a member of the Fletcher School's first class, entering in 1933 and earning a master's degree in 1937. He also earned a doctorate from Harvard University in 1938. He published "Treaty Relations of the British Commonwealth Nations" in 1939.

Surviors include his wife, the former Charlotte Fuller, of East Orleans; two sons, Robert F., of Lakewood, Colo., and Jay R., of Sacramento, Calif., and one grandaughter.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society, or to the Robert B. Stewart Library Fund, the Fletcher School of Law and Diplomacy, Tufts University, Medford, Mass.