THERE ARE no doubt thousands of people in federal prison who deserved a presidential commutation more than Roger Stone. But after President Trump’s intervention on Friday, Mr. Stone will serve none of his prison sentence. The president may have had the power to help his longtime friend. But that does not make it any less a perversion of justice — indeed, it is one of the most nauseating instances of corrupt government favoritism the United States has ever seen.

There is no doubt about Mr. Stone’s guilt. During the 2016 presidential campaign, he tried to play intermediary between WikiLeaks, which had become a front for the Kremlin, and the Trump campaign, which reaped the benefits of WikiLeaks’s publication of stolen Democratic emails. A jury concluded that Mr. Stone obstructed Congress, lied to investigators and tampered with a witness in the investigations that followed the 2016 race — “covering up for the president,” as the judge in his case noted.

Though Attorney General William P. Barr moved to reduce Mr. Stone’s sentencing recommendation after conviction, even he called the case against Mr. Stone a “righteous” prosecution. He was sentenced to 40 months in prison and was due to surrender on Tuesday — thus prompting Mr. Trump’s Friday night action.

As Mr. Trump discussed granting clemency to his criminal friend, Mr. Barr publicly defended the sentence, perhaps to prevent a mutiny among Justice Department staff who signed up because they believe in the rule of law, not the arbitrary rule of an unusually petty man in the White House.

Now, the department’s career investigators and prosecutors must absorb yet another insult to their profession from political leaders who abuse their trust. We can only sympathize with their impossible position. A Justice Department brain drain would only reduce fairness and competence in federal law enforcement. It would no doubt take years of rebuilding to reattract the talent that Mr. Trump’s rule has already repelled from the department, let alone to replace a late-term exodus of staff. Yet we can blame no one in the Justice Department for misgivings or feelings of complicity with a wayward presidency. We hope that the coming presidential election will soon offer them — and the nation that relies on them — relief.

The United States is supposed to be a place in which laws apply equally to all. And while it never has — and never will — live up to that ideal in full, no modern president before Mr. Trump has so clearly renounced it. The president seems to be doing his best, within the confines of the U.S. constitutional system, to emulate the gangster leadership of Russian President Vladimir Putin, a man whose ruinous reign Mr. Trump has always admired. If the country needed any more evidence, Friday confirmed that the greatest threat to the Republic is the president himself.

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