Clinton was far from a willing participant in his own investigation. He resisted in multiple ways. But he was constrained by an appreciation for the rule of law, even as he was trying to evade its consequences.

Consider, by way of example and comparison, Clinton’s use of executive privilege—a privilege that Trump has also invoked in recent days to frustrate the House’s effort to get the unredacted version of the Mueller report. Just what is executive privilege, and why do we have it?

Broadly speaking, the idea behind executive privilege is that we want the advice that senior officials give the president—which often involves matters of national security and domestic prosperity, and is of crucial importance to the nation—to be candid and complete. It hardly seems plausible that a president could do his or her job and fulfill constitutional obligations without the candid advice of senior advisers. Protecting the confidentiality of these conversations may foster more open communication and lead, in the end, to better results.

And so, executive privilege extends not just to the legal advice that the president receives but, at least in theory, to all of the many communications that take place within the executive branch that are intended to develop policy for the benefit of the president. As the Supreme Court said in United States v. Nixon while reviewing President Richard Nixon’s claim of privilege, there is a “valid need for protection of communications between high government officials and those who advise and assist them in the performance of their manifold duties.”

But it is abundantly clear that executive privilege (in all of its forms) is not absolute. That’s why Nixon ultimately lost his effort to prevent disclosure of the tapes he had made of conversations in the White House. Nixon asserted that the confidential nature of the conversations made all of them privileged against disclosure. The Court, however, rejected Nixon’s extreme reading that he had an absolute power to withhold the tapes:

To read the Article II powers of the President as providing an absolute privilege as against a subpoena essential to enforcement of criminal statutes on no more than a generalized claim of the public interest in confidentiality of nonmilitary and nondiplomatic discussions would upset the constitutional balance of “a workable government” and gravely impair the role of the courts under Article III.

And, one might add, it might also impair the role of Congress under Article I—as reflected in today’s debates between the president and the House of Representatives.

In effect, the Court created a balancing test: The more significant the investigative interest, the greater the likelihood that privilege will yield. In Nixon, a criminal investigation was seen as a high-value investigative interest. Today a congressional inquiry into presidential misconduct would be as well.