Executive privilege is the right of the Executive Branch to operate independently of Congress and the courts, and keep information developed within the Executive Branch confidential. The first use of executive privilege was made by the Founding Father George Washington in 1796. Congress demanded documents relating to the Jay Treaty but George Washington refused the demand based on executive privilege.
The purpose of executive privilege is to maintain separation of powers, and to protect diplomatic and military secrets.
President Harry Truman claimed Executive privilege after leaving office to avoid cooperating with HUAC and McCarthy Committee investigations.[1]
In United States v. Nixon (1973), the Supreme Court ruled that the president cannot absolutely refuse to turn over information wanted by the judiciary.
Executive privilege continues to be used by modern presidents in resisting demands for information.