Donald Trump’s lawyers have signaled he won’t agree to a voluntary interview with special counsel Robert Mueller. If Mr. Mueller insists, he will have to subpoena the president. To enforce a subpoena, the special counsel would have to go to court and meet a highly exacting standard, showing what he wants and why he needs it. He would be unlikely to succeed, given that Mr. Trump already has cooperated extensively with the investigation, producing 1.4 million documents and making dozens of White House staffers available for interviews.
The leading precedent is a 1997 opinion, In re Sealed Case, by the U.S. Circuit Court of Appeals for the District of Columbia. The case involved the independent counsel investigation of former Agriculture Secretary Mike Espy, who was accused of receiving unlawful gifts. The independent counsel sought to obtain sensitive documents produced in the course of an internal White House inquiry. These materials involved the preparation of a report to then-President Clinton himself. Although Mr. Clinton had directed that most of the materials be provided, he asserted executive privilege to withhold some items.
At issue in particular was information regarding whether Mr. Clinton should discipline or fire Mr. Espy, who did resign. To justify producing such sensitive materials involving “the exercise of [the president’s] appointment and removal power, a quintessential and non-delegable presidential power,” the court required the independent counsel to demonstrate with “specificity” why he needed the materials and why he could not get them, or equivalent evidence, from another source. (Mr. Espy was acquitted in 1998.)
Mr. Mueller’s initial charge was to investigate Russian interference in the 2016 presidential election and possible collusion between the Trump campaign and the Russian government. But his investigation has expanded to cover whether Mr. Trump has obstructed justice. The president’s critics say his obstructive acts include urging then-FBI Director James Comey to “go easy” on former national security adviser Mike Flynn, subsequently firing Mr. Comey, and his public criticism of Mr. Mueller, Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein.
There are significant factual disputes about these episodes, but all involve the president’s exercise of his core constitutional powers as chief executive, including the power to appoint and remove high-level executive-branch officials, to supervise the performance of their duties (as in the Espy case), and to determine law-enforcement priorities. We have argued in these pages that the president cannot obstruct justice by exercising the discretionary powers of his office, especially in determining whether and why to fire high-level presidential appointees like Mr. Comey. According to the two leaked letters from Mr. Trump’s lawyers to Mr. Mueller, they take essentially the same view.
Any prosecution based on Mr. Trump’s exercise of his core constitutional authority would dramatically impair the executive’s status as a coequal branch of government, considering that Congress enjoys immunity under the Speech and Debate Clause while exercising its legislative powers. It would also inject the judiciary into the president’s decision-making process, requiring judges to delve into matters that are inherently political.
Developments over the past year reinforce our view that it would unconstitutionally debilitate the presidency to base an obstruction charge on gainsaying the president’s motives in exercising his core responsibilities. Mr. Trump’s critics have also accused him of obstructing justice by using his pardon power. They claim his pardons of Joe Arpaio, Scooter Libby and Dinesh D’Souza —whom he considers victims of previous political prosecutions—were meant to reassure targets of Mr. Mueller’s probe that they too might be pardoned. Under such logic, a president under investigation could not discharge his constitutional duties at all, including the use of military force overseas—which can always be cast as a “wag the dog” strategy.
These considerations distinguish Mr. Trump’s situation from that of Mr. Clinton, who in August 1998 became the only sitting president to appear before a grand jury. That independent-counsel investigation did not concern the exercise of presidential authority. They concerned allegations of perjury and obstruction from Mr. Clinton’s personal relationship with a White House intern. Independent counsel Kenneth Starr subpoenaed the president but withdrew the subpoena when Mr. Clinton agreed to appear voluntarily by video. Because constitutional considerations were not in play, the In re Sealed Case analysis would not have favored the president. (The same might apply if New York-based federal prosecutors attempt to subpoena Mr. Trump in connection with Michael Cohen’s guilty plea on charges unrelated to presidential power, although there are other reasons why such a subpoena would neither be issued nor enforced.)
We also now know that Mr. Trump authorized White House counsel Don McGahn to answer all of Mr. Mueller’s questions regarding every alleged obstructive action. According to press reports, Mr. McGahn spent nearly 30 hours describing the substance of his conversations with Mr. Trump and offering his assessment that the president’s actions were lawful.
With access to the relevant documents and everyone around the president, the special counsel has no material facts left to find. Interviewing or interrogating the president could shed additional light only on his own thoughts and motives—exactly what executive privilege is designed to protect. They relate entirely to a constitutionally proscribed obstruction inquiry that would violate the separation of powers.
Applying the In re Sealed Case standard, Mr. Mueller cannot show that any need for Mr. Trump’s testimony outweighs the president’s interest in keeping his thoughts private. The president hasn’t asserted executive privilege vis-à-vis the special-counsel investigation. But if Mr. Mueller seeks his testimony directly, he can and should. Mr. Mueller knows that losing a subpoena court fight would prolong and delegitimize his investigation. He is unlikely to press the point.
Messrs. Rivkin and Casey practice appellate and constitutional law in Washington. They served in the White House Counsel’s Office and Justice Department under Presidents Reagan and George H.W. Bush.