In 1947, when Congress voted to create the CIA as part of the National Security Act, there was great concern about whether the CIA could operate in the United States and against Americans.
Congress wanted to assure the public that this agency would not lead to the growth of a secret police. Responding to these suspicions, Dr. Vannevar Bush, an administration witness, explained that the agency was concerned only with intelligence "outside this country," and not with "internal affairs. To make sure, Congress wrote into the ClA's charter that the agency was prohibited from exercising "police, subpoena, or law-enforcement powers or internal security functions." Congressional debate made it clear that Congress anticipated that the CIA would simply not operate at home.
Kutoka kwenye kitabu cha The Lawless States : The crimes of the U.S. Inteligence Agencies
by Morton Halperin, Jerry Berman, Robert Borosage, Christine Marwick.