Morton Rosenberg's "Presidential Claims of Executive Privilege: History, Law, Practice and Recent Developments"

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Executive privilege is the power claimed by the president and other members of the executive branch to resist certain subpoenas and other interventions by the legislative and judicial branches of government. The concept of executive privilege is not mentioned explicitly in the Constitution, but the Supreme Court ruled it to be an element of the separation of powers doctrine, and/or derived from the supremacy of the executive branch in its own area of constitutional activity. Various presidents – most infamously Richard Nixon – have invoked their right to executive privilege over a litany of issues they deemed to be private communications.

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