Special Prosecutor Robert Mueller’s swan song illustrates nothing so much as the constitutional illogic of having a special prosecutor set up to investigate the president in the first place. Mr. Mueller sought to create the impression that he was doing everything by the book. He was, though, playing against Washington, Madison, Adams, and the other Framers of the Constitution. So it ended in checkmate.

That has been our concern throughout this whole affair. It is not a partisan thing with us. We have been arguing since the days of Nixon against anything that smacks of independence from the president of any prosecutor. It was our view when Judge Walsh was sicced on Presidents Reagan and George H.W. Bush, during Judge Starr’s long pursuit of President Clinton, and Mr. Mueller’s mission against President Trump.

All these probes or prosecutions were crosswise with the logic of the Constitution. Only the president is authorized and required to take care that our laws be faithfully executed. To ensure he is able to do that, only the president is given the power to commission the officers of the United States. It is why there is a grant of authority to the Representatives House to investigate a president and forward to the Senate articles of impeachment.

It is also why the Framers established that “Judgment in Cases of Impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States.” Yet it’s why they also established that if a president is removed from office through impeachment, his immunities end and he “shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.”

Throughout this drama, we have lurked in a small minority — perhaps of one — arguing that the President should have fired Mr. Mueller the moment he learned of his appointment. He should have done so precisely because the president didn’t commission him. The president’s grant of authority is to commission all the officers of the United States. The grant is made in the same sentence about how he shall take care that the laws are faithfully executed.

Watching Mr. Mueller try to weave and dodge his way through this part of the Constitution, well, it was like watching Spassky go down to defeat in Iceland. Mr. Mueller was trapped by the very document to which he was sworn. There are those who reckon — and we don’t gainsay their judgment — that firing Mr. Mueller would itself have put Mr. Trump on the brink of impeachment. If the liberal foghorns are correct, though, the president is on the brink of impeachment anyhow.

So why didn’t Mr. Trump fire Mr. Mueller at the start? Aye, that’s a question. Our guess — we offered it in an editorial called “The Mueller Firing Speech” — is that the president acquiesced in Mr. Mueller’s initial work because he believed that he was not a target of the investigation. By the time he realized that he was, it was too late. His own White House counsel was threatening to disobey what we deem (again, we’re in a minority) a lawful order.

It’s too soon to tell whether the House will impeach Mr. Trump. We hope not. It’s not too soon to say, though, that it’s time for reforms to prevent the Justice Department from ever again turning on the sole officer empowered to take care that our laws are faithfully executed. The only route to taking power away from the President has to start in the House. It’s an irony that this whole thing is before the House precisely because the president didn’t obstruct the investigation.