John Yoo: Mueller left a gap. Barr just filled it.

The logic here is breathtaking: The president can end an investigation on the basis that he is “falsely accused.” The entire point of an investigation is to determine culpability; if the president can end an investigation into himself or any of his allies simply by asserting his own innocence, then he is effectively above the law. Under this standard, President Richard Nixon was perfectly within his rights when he attempted to end the investigation into the break-in of Democratic headquarters at the Watergate, which implicated several of his campaign operatives and ultimately led to his resignation.

Barr has previously suggested investigating the officials involved in the Trump inquiry for wrongdoing; on Wednesday, he was evasive when Senator Kamala Harris asked whether the White House had ever asked him to prosecute anyone. Should Trump demand that his attorney general prosecute the next Democratic nominee for president, there’s little evidence that Barr would be any kind of obstacle. The attorney general is sworn to uphold the Constitution, not to act like a mob enforcer against the president’s political enemies.

Nixon famously declared in 1977, in an interview with the reporter David Frost, that “when the president does it, that means that it is not illegal.” That was not mere sophistry, but ideology, and it is an ideological strain that has run through nearly every Republican administration since Nixon.

Barr’s involvement in the Iran-Contra scandal helps illuminate his conduct today. The administration of President Ronald Reagan defied federal law by selling arms to Iran in order to fund right-wing guerrillas in Central America, a scandal that led to the appointment of an independent counsel and the convictions of several high-ranking administration officials. When George H. W. Bush took office, he pardoned six officials implicated by the investigation at Barr’s urging.

The Iran-Contra scandal itself speaks to the conception of executive power to which Barr subscribes: that a president can do whatever he wants, even if Congress bars him from doing so, particularly if he is acting in what he believes to be the interests of the country—Trump is famously incapable of distinguishing between national interests and personal ones, between loyalty to him and loyalty to the nation. As Reagan’s former national security adviser Robert McFarlane put it, Reagan “just didn’t believe that it was a legitimate authority of the Congress to say that—that he, rather than the Congress, determined how he would conduct, in this case, the support of the freedom fighters.”

David Frum: Trump’s stonewall is beginning to crack

This has been particularly true of the expansive conservative conception of the president’s constitutional war-making powers. If Reagan openly defied Congress and the law, the first President Bush ratified his actions by pardoning those involved in the scheme. The next Republican president, George W. Bush, covertly defied the law by building a network of secret prisons across the globe, indefinitely imprisoning those suspected of terrorism, and sanctioning warrantless surveillance of American citizens, all based on dubious legal theories that amounted to little more than Nixon’s insistence that the president is above the law. Less articulate was the former George W. Bush Justice Department official John Yoo’s response to being asked whether the president could order a child’s testicles crushed: “I think it depends on why the president thinks he needs to do that.”