William H. Schaap, a radical lawyer, author and publisher who fought against investigative abuses by government agencies at home and abroad, died on Feb. 25 in Manhattan. He was 75.

The cause was pulmonary disease, his niece Rosie Schaap said.

Mr. Schaap began his activism in law school, counseling students arrested in Chicago for protesting segregated housing.

As a lawyer, he defended Columbia University students arrested in 1968 for occupying campus buildings to protest the war in Vietnam. In the late 1960s, he left a Wall Street law firm where he was an associate and moved to Japan and Germany with his wife, Ellen Ray, to counsel resisters to the war in Vietnam.

In 1976, they formed what became CovertAction, a publication that reported on illegal Central Intelligence Agency activities. It also identified C.I.A. agents by name, from unclassified sources, a practice outlawed by Congress in 1982. Mr. Schaap also represented C.I.A. whistle-blowers, like Philip Agee.