For four years, Donald Trump’s interpretation of his powers made up in pithiness what it lacked in nuance: “I have an Article II, where I have the right to do whatever I want as president.” Now, having refined his jurisprudential thinking, he proposes an expansive wrinkle on his already capacious conception of presidential prerogatives: He should have the power, unconditionally and forever, to invoke executive privilege regarding communications — documents and conversations — he had with others while in office, regardless of who seeks access to them, or the reasons for so seeking. His motive in resisting inquiries from the House select committee investigating events that culminated in the Jan. 6 attack on the Capitol is, he says, a selfless one: “defense of the Office of the Presidency.”

The power of executive privilege is not mentioned in the Constitution. Although the first president sometimes withheld information from Congress, a “privilege” to do so was first named and forthrightly asserted (by another general turned president) in mid-20th century. And although the Supreme Court has acknowledged its existence, its nature and scope have not yet been satisfactorily articulated by the few judicial examinations of particular presidents’ denials of information to Congress.

There is a common-sensical consensus that presidents while in office need some secrecy to encourage candid advice. And sitting presidents, probably with their post-presidencies in mind, have supported some predecessors’ claims of executive privilege.

Stanford law professor Michael W. McConnell, in “The President Who Would Not Be King: Executive Power Under the Constitution,” writes that James Madison considered what presidential privileges were proper because he worried that the executive branch might “be at the mercy of the legislative.” This is hardly germane today, with a frequently supine Congress eagerly shedding discretion to the executive.

McConnell says that because the Constitution gave Congress no enumerated power to compel testimony, Madison’s remarks about explicit presidential privileges were set aside. McConnell notes that early executive-legislative skirmishes over information were couched in language about congressional “requests” for information that implicitly acknowledged presidential authority, not subpoenas that derogated it.

University of Virginia law professor Saikrishna Bangalore Prakash argues (in “Imperial from the Beginning: The Constitution of the Original Executive”) that although there is no constitutional privilege of presidential privacy, neither is there a constitutional authority for Congress to demand information. In his “The Living Presidency: An Originalist Argument Against Its Ever-Expanding Powers,” Prakash says one purpose for the increasing frequency of executive refusals to comply with congressional demands for information and testimony is “stymieing congressional investigations of the executive”: President Dwight D. Eisenhower, who invented the phrase “executive privilege,” did so to thwart Sen. Joseph McCarthy’s reckless rummaging in Eisenhower’s administration, including the Army.

Courts have been judiciously reluctant to referee tussles between the political — the legislative and executive — branches. And there are different considerations when the issue is compromising presidential privacy by subpoenas from courts in criminal proceedings, and by subpoenas from congressional committees performing oversight with possible legislative outcomes.

But that judicial reluctance, reflecting a Madisonian assumption, is outdated. Madison assumed that a powerful human constant, ambition, would result in creative tension — and, ideally, equilibrium — between the political branches: “Ambition must be made to counteract ambition. The interest of the man must be connected with the constitutional rights of the place.” (Federalist 51) Madison’s assumption has been largely nullified by party loyalties: Most members of Congress subordinate their institution’s interests and prerogatives to those of a president from their party.

Given today’s political tribalism, were both houses of Congress controlled by the previous president’s party, there would be no Jan. 6 investigation. And there will barely be an investigation if the judiciary allows Congress to be neutered by an ex-president’s successful assertion of a presidential “privilege” so sweeping that it even shields Stephen K. Bannon. His seven months on the president’s staff ended almost 41 months before the events of Jan. 6, in the run-up to which he seems to have been involved.

If there is to be a timely and thorough investigation of the Jan. 6 assault on Congress’s constitutional function of certifying electoral votes, and of Trump’s role before and during this, congressional committees should have what private parties have — standing to seek judicial enforcement of compliance with subpoenas. If we are to “recage the executive lion” (Prakash’s phrase), and encourage Congress to recover its dignity and enable it to perform its oversight duties, the judiciary must temper its reluctance to intervene.