Ernest L. Kerley, 50, an assistant legal adviser with the State Department who had worked there for more than 25 years, died Wednesday at Fairfax Hospital of complications following brain surgery.

Mr. Kerley joined the State Department's office of the legal adviser in 1956. He was promoted to assistant legal adviser in 1966, and worked on international claims. In 1971 he began working on United Nations affairs.

From 1963 to 1965, he was on the legal staff of the International Atomic Energy Agency (IAEA) in Vienna, Austria. He then rejoined the State Department.

He was the author of a number of articles on international law for legal journals.

Mr. Kerley was born in Cincinnati, Ohio, and moved to this area in 1956. He earned bachelor's and law degrees at the University of Cincinnati, and another degree, in international law, at Harvard University.

He served in the Army during the Korean conflict.

He is survived by his wife, Betty, of thehome in Reston; a son, Edward, a student at the University of Cincinnati; two daughters, Barbara, a student at the University of Chicago, and Ruth, a Peace Corps worker inKenya, and a sister, Mary Jane Wilkinson, of Albany, Ind.