The White House, Executive Order 11905: United States Foreign Intelligence Activities, 41 Fed. Reg. 7703 (Feb. 18, 1976) (full-text).
This Executive Order established policies to improve the quality of intelligence needed for national security, to clarify the authority and responsibilities of the intelligence departments and agencies, and to establish effective oversight to assure compliance with law in the management and direction of intelligence agencies and departments of the national government.
In particular, this Executive Order formally prohibited the CIA from using electronic or physical surveillance to collect information about the domestic activities of Americans and banned the National Security Agency from intercepting any communication made within, from, or to the United States, except lawful electronic surveillance under procedures approved by the Attorney General.