Isidore H. Wachtel, 70, a Washington lawyer who specialized in government contract law, died of cancer Friday at Georgetown University Hospital.

He was a senior partner in the firm of Wachtel, Ross and Matzkin. He had helped found the predecessor firm in 1947 and had remained with it until his death.

Mr. Wachtel was an advocate in a landmark case, in which the Supreme Court sharply limited the power of the president to remove from office judges and those performing judicial functions.

Mr. Wachtel was born in New York City. He attended New York University and graduated from Brooklyn Law School in 1932.

He was assistant general counsel to the New York Housing Authority in the late 1930s and then became an enforcement attorney with the Office of Price Administration in 1942-43 and counsel with the Reconstruction Finance Corporation from 1943 to 1947.

In 1963, Mr. Wachtel was coauthor of a multivolume treatise on public contract law, "Government Contracts," which has been widely cited as an authority in federal courts.

He was a member of the D.C., Federal and American Bar Associations. He belonged to the National Lawyers Club, the University Club, the Capitol City Club, Binai B'rith and Indian Spring Country Club.

He is survived by his wife, Sophie, of the home in Washington; a son, Burton M., of Vienna, Va.,; a daughter, Susan N. Irwin, of Bethesda; a brother, Harry, of New York City, and three sisters, Elsie Wachtel and Pearl Bluman, both of New York City, and Nettie Lessner, of Tucson.

The family suggests that expressions of sympathy be in the form of contributions to the Sloan Kettering Institute or the American Cancer Society.