This piece was originally published on Just Security, an online forum for analysis of U.S. national security law and policy.

Before Pentagon official Laura Cooper testified before the House Intelligence Committee, she received a stern warning from David L. Norquist, the deputy secretary of defense, urging her against speaking with impeachment investigators. Among other things, Norquist cautioned Cooper against participating without Defense Department counsel present to protect “against the improper release of … material covered by the executive privilege which is the President’s alone to assert and to waive.”

Cooper went ahead and testified, as have a number of other former and current executive branch officials from the departments of State and Defense and the National Security Council staff, all in the face of similar admonitions. It is not clear if Cooper or the others who have provided testimony were concerned about the executive privilege issue, but no matter: The privilege presents no bar to such testimony in the context of a presidential impeachment investigation—and, following the Thursday resolution, there should be no doubt that the House is engaged in an impeachment inquiry.

There are three reasons why executive privilege is not an impediment to the appearance of any witness before the House Intelligence Committee in the context of an impeachment inquiry. First, history suggests that, where the authority of the House to investigate the president is concerned, impeachment is different. Presidents have claimed from the earliest days of the republic that they have a protectable interest in the confidentiality of communications with their advisers. In 1786, for example, George Washington famously declined to turn over certain papers related to the Jay Treaty—but, as professor Jean Galbraith has observed, Washington carved out a specific exception: when the House has the “purpose … of an impeachment.” His advisers agreed that executive privilege ought not apply to impeachment.

There are three reasons why executive privilege is not an impediment to the appearance of any witness.

The second reason why executive privilege does not apply in the impeachment context flows from the Supreme Court’s 1974 decision in United States v. Nixon. There, the court considered the question of whether this privilege protected from disclosure information sought in connection with an ongoing federal criminal proceeding. As an initial matter, the court observed that the importance of full candor from the president’s advisers “is too plain to require further discussion.” It follows that the need to prevent disclosure of such communications drives the privilege to ensure the president is not denied the honest counsel he needs to undertake the various duties and responsibilities of the office.

But this justification for the privilege falls short when the potential for disclosure does not spring from a judicial proceeding or as a result of congressional oversight of federal programs. Litigation involving a president’s official actions is not uncommon, and both houses of Congress regularly engage in legitimate oversight efforts. Both kinds of proceedings occur with sufficient frequency that the underlying purpose of executive privilege—candid advice and counsel—would be threatened by the potential opportunities for the disclosure of all manner of presidential communications.

Again, presidential impeachment is substantively different. It is so comparatively infrequent—the current effort represents just the fourth time in the nation’s history that the House has launched presidential impeachment proceedings—as to make it unlikely that advisers would, in the words of the Nixon court, “temper candor with a concern for appearances” in communications with the president. Perhaps more important, an impeachment inquiry into presidential conduct is readily distinguishable from both litigation and ordinary legislative oversight: It is exclusively focused on the person of the president, as opposed to the resolution of a civil or criminal dispute or the efficacy of the president’s policy choices. Impeachment, in other words, concerns matters outside the public policy considerations that underlie the need for executive privilege. This view finds support in the recent scholarship of Jonathan Shaub, who has made a similar argument, and in the Watergate-era decision by the U.S. Court of Appeals for the D.C. Circuit in Senate Select Committee v. Nixon, which suggests that an impeachment inquiry represents an extraordinary, and constitutionally authorized, kind of legislative oversight.

Third, even assuming that the animating rationale for the privilege embraced by the Nixon court applies in the impeachment context, still the need for the information sought should outweigh the privilege. In Nixon, for example, the court concluded that the integrity of the criminal justice system required the production of the information sought for inspection. Given that a presidential impeachment inquiry is in the nature of a criminal investigation, as Mike Stern has argued, assertions of executive privilege should be outweighed in the impeachment context as well.

To be sure, the Nixon court noted that its analysis might have been different had the president’s claim of privilege related to “military, diplomatic, or sensitive national security secrets,” which may be shielded from disclosure in judicial proceedings. But an impeachment investigation is not a judicial proceeding—it is a constitutional prerogative of the House of Representatives and within the House’s sole discretion. When, as is true of the current inquiry into President Donald Trump’s dealings with Ukraine, the core of the investigation implicates both foreign policy and national security, it would make no sense for executive privilege to shield relevant communications from disclosure. Such an application of the privilege would deny the House access to the very information it needs to determine whether to move forward with impeachment—it could effectively make the president unimpeachable when operating in this wide arena, a result at odds with the plain text of the Constitution.

What all of this means is that the witnesses summoned to appear before the House Intelligence Committee should not view executive privilege as standing in the way of their testimony. Assuming executive privilege applies in the impeachment context, moreover, it is clear that the House’s need for information outweighs the president’s interest in confidentiality, even in communications that may relate to foreign policy or national security.

We should remember the Nixon court’s admonition that executive privilege is neither absolute nor unqualified. To conclude otherwise today would fatally undermine the House’s authority to hold a president in check when there is considerable reason to believe he or she may be responsible for high crimes or misdemeanors.

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