The right of executive privilege is not directly granted to the president in the Constitution. Instead, it has historically been considered to be a right implied by the constitutional principal of separation of powers between the three branches of government.
Reasons for Claiming Executive Privilege
Historically, presidents have exercised executive privilege in two types of cases: those that involve national security and those that involve executive branch communications.
Presidents most often claim executive privilege to protect sensitive military or diplomatic information, which if disclosed, could place the security of the United States at risk. Given the president’s constitutional power as commander and chief of the U.S. Military, this “state secrets” claim of executive privilege is rarely challenged.
Executive branch communication
Most conversations between presidents and their top aides and advisers are transcribed or electronically recorded. Presidents have contended that executive privilege secrecy should be extended to the records of some of those conversations. The presidents argue that in order for their advisers to be open and candid in giving advice, and to present all possible ideas, they must feel safe that the discussions will remain confidential. This application of executive privilege, while rare, is always controversial and often challenged.
In the 1974 Supreme Court case of United States v. Nixon, the Court acknowledged "the valid need for protection of communications between high Government officials and those who advise and assist them in the performance of their manifold duties." The Court went on to state that "[h]uman experience teaches that those who expect public dissemination of their remarks may well temper candor with a concern for appearances and for their own interests to the detriment of the decision making process."
While the Court thus conceded the need for confidentiality in discussions between presidents and their advisers, it ruled that the right of presidents to keep those discussions secret under a claim of executive privilege was not absolute, and could be overturned by a judge. In the Court’s majority opinion, Chief Justice Warren Burger wrote "[n]either the doctrine of separation of powers, nor the need for confidentiality of high level communications, without more, can sustain an absolute, unqualified Presidential privilege of immunity from judicial process under all circumstances."
The ruling reaffirmed decisions from earlier Supreme Court cases, including Marbury v. Madison, establishing that the U.S. court system is the final decider of constitutional questions, and that no person, not even the president of the United States, is above the law.