The House didn’t need the papers for any “purpose under [its] cognizance”; the only possible such purpose, Washington said, would be “that of an impeachment, which the resolution has not expressed.”

Thus, at the very birth of what we today call “executive privilege,” Washington admitted that the privilege might have an exception—the power of impeachment granted to the House by the Constitution. In the years since, presidents and members of Congress have often said that when the House acts as part of an impeachment inquiry, the executive must yield to its demands for information. John Tyler, the first president subjected to a formal impeachment inquiry (which came to nothing), turned over such demanded documents after the House committee pointed out that impeachment required the power to compel “the production of all such papers as may be necessary to prove the charges on which the impeachment is founded.”

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James K. Polk, not ordinarily known for his good humor, nonetheless “cheerfully admitted” that

In [an impeachment] case the safety of the Republic would be the supreme law, and the power of the House in the pursuit of this object would penetrate into the most secret recesses of the Executive Department. It could command the attendance of any and every agent of the Government, and compel them to produce all papers, public or private, official or unofficial, and to testify on oath to all facts within their knowledge.

The term executive privilege, meaning the privilege to shield certain testimony and documents from disclosure to courts or congressional investigators, did not come into use until the Eisenhower administration; Richard Nixon was the first and so far only president to assert such a privilege against a formal impeachment inquiry. That attempt, as we all know, ended badly in 1974, when the Supreme Court—including three of his appointees—decided that he must turn over the famous “smoking gun” tape to the U.S. District Court for use in a criminal proceeding against seven members of his White House team who had overseen the Watergate burglary and cover-up:

We conclude that when the ground for asserting privilege as to subpoenaed materials sought for use in a criminal trial is based only on the generalized interest in confidentiality, it cannot prevail over the fundamental demands of due process of law in the fair administration of criminal justice. The generalized assertion of privilege must yield to the demonstrated, specific need for evidence in a pending criminal trial.

The case was a resounding victory for the rule of law. It was also the death knell for Nixon’s presidency. Within two weeks of turning over the tapes, the 37th president was en route to San Clemente, California, and the 38th, Gerald Ford, had taken the oath.