Is President Trump the only one in Washington who has read the Constitution? Forgive us, but that’s how, amid the brouhaha over Mr. Trump’s criticism of the Justice Department, we would turn around the question that Khizr Khan famously asked at the 2016 Democratic National Convention. The president, it seems, has a clearer grasp of his constitutional powers and obligations than anyone in this fray.

The thing to focus on is Article II of the Constitution itself. It creates the president and vests in him — and him alone — the executive powers of the government. It’s as straightforward as it can be. “The executive Power,” it says, “shall be vested in a President of the United States of America.” It doesn’t say “some of the executive power.” It says “the” executive power. It vests such power in only the president.

Article II also creates the presidential oath, which bears parsing. It binds the president to preserve, protect, and defend the Constitution — but not absolutely. He’s required to do the preserving, protecting, and defending only, as he is required to put it, “to the best of my ability.” This is no doubt a minority opinion, but we take that to mean that a president can be imperfect. Or, to put it another way, he’s entitled to some mistakes.

In any event, the fact that the executive power is vested in a single person makes the executive branch different from the legislative branch, where powers granted are diffused among 535 members of the House and Senate, and judicial branch, where power is diffused among 870 Article III judges. One thing this means is that, unlike judges and legislators, presidents can’t recuse themselves for a conflict of interest.

This is known in law as the rule of necessity. Presidents must proceed and do their duty, to the best of their ability, even when it’s awkward, as it certainly is in the case of, say, Roger Stone, the subject of the latest presidential tweetstorm. The rule of necessity doesn’t mean that presidents can act out of corrupt motives. It does mean they must, to the best of their abilities, take care that the laws are faithfully executed.

As we read the Constitution, that means that if Mr. Trump doesn’t like the way the Justice Department is dealing with Mr. Stone, or anyone else, he has to do his best to correct it — even maybe by tweeting some guidance or assigning the matter to a different prosecutor. In the case of Roger Stone, Attorney General Barr was already on top of the runaway prosecutors. Mr. Trump, though, was entitled to his tirade.

The one constitutional error the President made was his response to Mr. Barr’s interview in which the AG said the president “has never asked me to do anything in a criminal case.” The President’s error was then to say: “This doesn’t mean that I do not have, as President, the legal right to do so, I do, but I have so far chosen not to!” That strikes us as constitutionally off.

Presidents, after all, don’t have any special “rights.” They have no more rights than your average dustman, washroom attendant, or newspaperman. What presidents get are power (the “executive power”) and duties, in this case the obligation to take care that our laws are faithfully executed. If he thinks the prosecutors are going too hard on his friend, he has a duty to act.

And twitter is not Mr. Trump’s only constitutional power. He could commute any sentence Roger Stone draws. Or clear him completely, via a pardon. He could do that even before any sentence is handed down. He doesn’t need to consult a soul. The pardon is the least fettered power the President has. Does this mean our greatest newspapers are wrong to suggest that the President is sometimes his own worst enemy? Not at all. That, though, is a not a constitutional cavil but a political one, just as was Khizr Khan’s.