When Conrad Black stood before a federal judge in Chicago to hear his final prison sentence, all that was left of the fraud case against him was a single count. He was given a chance to make a statement. “I never ask for mercy,” he told the judge, “but I do ask for avoidance of injustice.” It was a sad thing for our country and for newspaperdom, we wrote at the time, that his request was denied.

All the greater the glory today, when President Trump reached for the ultimate tool our Constitution provides for the crafting of justice. The president used his pardon power to void the injustice in a case that should never have been launched. In the constitutional and legal sense, the pardon makes things the same as if Conrad Black had never been convicted at all.

There was never a moment in this case that we doubted Conrad Black’s innocence. Nor was that simply because his company was one of the founding partners in The New York Sun and he one of its founding directors. He’d already sold his interest and resigned from the Sun’s board. Nor was it because — as Humphrey Bogart put it — “he was your partner, and you’re supposed to do something about it.”

We defended Conrad Black because the case had all the earmarks of a wrongful prosecution. We’d learned to recognize them via a newspaper career covering, among other things, white-collar crime and constitutional questions. Nearly all of the charges were the kind of spaghetti prosecutors throw at a wall. A jury acquitted Lord Black of all those spaghetti charges.

It was the core charges — honest services fraud — that were the greater injustice. That’s because honest services fraud is a) impossibly vague and b) therefore almost impossible to defend against. We sketched that in an editorial when, after being convicted, Lord Black launched his appeal. The law of honest services fraud was, we argued, so vague as to be unconstitutional.

In the event, the Supreme Court said exactly that. It did so in the case of an ex-executive of Enron. Same day on the same issue, the nine justices vacated Lord Black’s conviction. The vote was unanimous. Justice Clarence Thomas agreed with Justice Ruth Bader Ginsburg, who wrote the opinion. Yet, incredibly, a lower court judge restored one of the counts, and Lord Black was returned to prison.

Lord Black bore up under all this with an epic display of grit. In prison, sometimes under squalid conditions, he wrote important books. He helped educate other inmates in history. When he was convicted, we had gathered the staff of the Sun and spoke to them of the strands of honor. We expressed to them the hope that Conrad Black would write a column from prison.

“Please treat any of his dispatches as coming from a man who made your newspaper possible,” we said, “and, when you edit his prose and put it into print, remember that the honor is ours.” That’s how we feel about it. In recent years, Conrad Black has used his column to defend President Trump — for all the right reasons. He’s sought to protect the decision of the voters to make Mr. Trump president.

No doubt the cynics are going to question the president’s motives in granting the pardon. We encourage them to focus on the facts of the case — why a jury acquitted Lord Black on most of the counts against him and why the remaining fraud counts were vacated by the Supreme Court. In granting the pardon, President Trump spoke of all that and of Lord Black’s “exceptional character.” It’s wonderful to see justice finally done.