William Barr is a heroic figure. At age 69, he returned to the Justice Department as attorney general some 26 years after his last tenure in that job, and in doing so he stepped into one of the most furious and nasty periods of political contention in U.S. history. In joining forces with President Trump, he subjected himself to vilification, denigration, and severe condemnation for nearly two years. Through it all, he never lost his calm demeanor as he defended himself and his philosophy of government with measured clarity.

Even in announcing his early departure from the Trump administration, effective December 23, Barr came under withering attack. Typical was a thrust on the Esquire website by a writer named Charles P. Pierce, who called Barr’s resignation letter “insufferably self-important and cloyingly obsequious.” He added that Barr served an administration “that most closely resembled Bonnie and 50 Clydes.” In other words, Barr is a crook and a violent one at that.

Ultimately, the independence of mind that characterized Barr’s approach to his job (never acknowledged or appreciated by his critics) got him crosswise with his own boss, the president, who gigged Barr for not manipulating a criminal investigation to influence the presidential election and for stating, correctly, after the voting that his investigators didn’t find voter fraud of a magnitude that would have overturned the outcome. So after taking abuse from the president’s liberal critics for defending the president, Barr took abuse from the president for not defending him sufficiently.

Why would anyone with Barr’s distinguished record re-enter public service at his age with full knowledge that it meant taking a level of abuse that most people seek to avoid at all costs? The answer seems to be that it was a matter of conviction. Barr felt that the office of the presidency, as established and defined by the Constitution, was in danger of being undermined and enfeebled by the president’s opponents through the investigation by special counsel Robert Mueller.

A key to understanding this concern was Barr’s memo of June 8, 2018, to Deputy Attorney General Rod Rosenstein that questioned what seemed to be emerging as Mueller’s basis for pursuing obstruction-of-justice allegations against Trump. In 19 tightly argued pages Barr explained why this development posed serious constitutional questions regarding separation of powers. He called Mueller’s obstruction theory “fatally misconceived.”

Mueller was of course the darling of the anti-Trump forces, and Barr’s apostasy marked him immediately as a bad guy. When the memo was released after Trump nominated Barr for attorney general, Chicago Law School professors Daniel Hemel and Eric Posner promptly attacked, saying the memo “seriously damages [Barr’s] credibility and raises questions about his fitness for the Justice Department’s top position.” An Obama administration lawyer named Marty Lederman accused Barr of advocating “absolute” and “all-encompassing” constitutional authority over actions by executive branch law enforcement officials.

Lederman’s portrayal of Barr’s point of view was erroneous. In fact, Barr made clear that a president or his officials can come under investigation if they commit “bad acts” designed to subvert the integrity of a legal proceeding. “Obviously,” he writes, “the President and any other official can commit obstruction in this classic sense of sabotaging a proceeding’s truth-finding function”—for example, if they knowingly destroy or alter evidence, suborn perjury, or induce a witness to change testimony. Indeed, both presidents Nixon and Clinton came under scrutiny for just such bad acts involving the impairment of evidence, and Barr considered both instances to be entirely appropriate.

But, argued Barr, the president enjoys certain plenary powers, granted by the Constitution, over law enforcement actions, such as his “complete authority” to exercise prosecutorial discretion on questions of whether to pursue a particular case or his prerogative of dismissing executive branch personnel. When such authority produces actions that get defined as bad acts of obstruction, argued Barr, the president becomes susceptible to a kind of political harassment that undermines his constitutional authority. “All that is needed is a claim that a supervisor [under the president’s authority] is acting with an improper purpose and any act arguably constraining a case—such as removing a U.S. attorney—could be cast as a crime of obstruction.”

It isn’t difficult to see how this could disturb the equilibrium of powers painstakingly crafted by the Founders. But what about a case in which the removal of an official could actually impede an investigation? One precipitating event in the Mueller probe, for example, was Trump’s firing of FBI director James Comey, who was pursuing a possible perjury case against Trump’s briefly installed national security adviser, Michael Flynn.

No, argued Barr, the president’s authority to fire Comey was absolute. The president, he said, “is the sole repository of all Executive powers conferred by the Constitution. Thus, the full measure of law enforcement authority is placed in the President’s hands, and no limit is placed on the kinds of cases subject to his control and supervision.”

But with authority comes responsibility. The Barr concept of the “unitary president,” in which the chief executive has full jurisdiction over executive decision-making, confers upon him also “the active obligation to supervise that goes with it,” as the Supreme Court noted in a 2010 case cited by Barr. To those who might argue that the president needs to be held accountable in a more direct and detailed manner, Barr maintained that the Founders, in granting broad discretion of action to the president, also granted counterforce prerogatives to the people and Congress, to maintain accountability. “Thus,” he wrote, “under the Framers’ plan, the determination whether the President is making decisions based on ‘improper’ motives or whether he is ‘faithfully’ discharging his responsibilities is left to the People, through the election process, and the Congress, through the Impeachment process.”

Barr’s view of the constitutionally protected prerogatives of the president, even when his own interests are at issue, may be debatable, with reasonable people coming to disparate conclusions. But it hardly constitutes an assault on the Constitution or a dangerous opening for executive abuse. And yet in these highly charged times, his studious argument was widely dismissed as beyond the pale. 

But for separation of powers to work as conceived, the president must be able to protect his political interests and constitutional prerogatives. If he can’t fortify his presidency against institutional encroachment, he can’t govern. And if executive-branch power centers emerge that he can’t control, then he is no longer master of his administration. And separation of powers inevitably will erode, perhaps even crumble. 

Barr’s argument, far more detailed and nuanced than I can capture here, stands as a monument of thinking on a complex matter of crucial significance to the republic. He is to be commended as well, upon his departure, for his political courage in standing up to his bitter and often malicious critics, for bringing propriety and sound management to a Justice Department that had been beset by political corruption, and for the example of a smooth, firm persona that never descended to the level of his would-be tormenters.

Robert W. Merry, longtime Washington, D.C., journalist and publishing executive, is the author of five books on American history and foreign policy.