Have you ever read an opinion article with which you're in general agreement but find yourself disagreeing sharply with some of the writer's points? That's how I felt about today's Wall Street Journal article by Judge Michael Ponsor about sentencing.

Judge Ponsor hails the 2010 Fair Sentencing Act, which reduces the discrepancy between sentences for crack cocaine and powder cocaine, and the 2005 Supreme Court decision in U.S. v. Booker, which overturned the federal sentencing guidelines.

The judge has something of an institutional bias: judges of just about any ideological or political background can cite cases in which sentencing guidelines or mandatory minimum sentences forced them to impose sentences that they believed were, in the circumstances of particular cases, unjust. I suspect that most of us in their places would agree. I'm sympathetic to Families Against Mandatory Minimums (despite their use of a non-Latin plural), an organization which argues against such sentences.

But that doesn’t mean they were a bad idea in the first place. Judge Ponsor, who was appointed a federal magistrate in 1984 and a federal judge in 1994, is apparently of a different view:

In 1984, at the start of my career, 188 people were imprisoned for every 100,000 inhabitants of the United States. Other Western industrialized countries had roughly equal numbers. By 2010 that figure had skyrocketed to 497 people imprisoned in the U.S. for every 100,000 inhabitants. Today, we imprison more of our people than any other country in the world.

How did 'the land of the free and the home of the brave' become the world's biggest prison ward? The U.S. now houses 5 percent of the world's population and 25 percent of its prisoners. Either our fellow Americans are far more dangerous than the citizens of any other country, or something is seriously out of whack in the criminal-justice system.

In fact, in the 1980s there was good reason to believe that Americans were far more dangerous than citizens of any other country. Violent crime rates roughly tripled between 1965 and 1975 and remained at a high plateau until the mid-1990s, spiking upward during the crack cocaine epidemic in the late 1980s.

One reason U.S. crime rates were so high was that many judges issued light sentences to defendants who, once released, became repeat offenders. It was not obviously unjust, in those circumstances, for legislatures and executives to fetter judges’ discretion by imposing mandatory minimums.

Nor was it obviously unjust to impose higher penalties on crack cocaine than powder cocaine at a time when there was plenteous evidence that the crack epidemic was leading to ancillary violence and that mothers addicted to crack were neglecting their children. Powder cocaine did not seem to producing similarly undesirable effects so frequently.

My argument is that the policies Judge Ponsor complains of were, at least arguably, needed and that they served their intended purpose. They kept dangerous people off the street and thus contributed to the sharp drop in crime in the 1990s and 2000s. To the point, I believe, that they are no longer needed today.

Most crimes are committed by young men. Criminals who were 21 when Judge Ponsor ascended to the bench turn 51 this year. Few are likely to offend again. And crime rates among the 21-year-olds of today are far lower than those of their counterparts in 1984.

Better law enforcement methods, like those introduced by New York Mayor Rudolph Giuliani and NYPD Commissioner William Bratton in 1994, undoubtedly play some role in this. And I suspect that the young males of today have a different mindset than their equivalents in 1984.

Congress legislates not for all time, but according to circumstances as they exist; when circumstances change, it may be time to reconsider and legislate again, in another direction.

So I tend to agree with Judge Ponsor when he laments that “defendants sentenced before the [2010 Fair Sentencing Act] was passed still languish today, serving out sentences that virtually all members of Congress now recognize as excessive.” This is indeed an anomaly and seems unjust.

But I disagree sharply with his next sentence. “And there is not a darn thing anyone can do about it.” But there is someone who can do something about it, even in Congress does not follow the judge’s suggestion and pass a law scaling back those sentences.

That person is President Obama. The president can pardon any offender and he can also commute part of a sentence, as George W. Bush did when he commuted Scooter Libby's jail term but declined to extend a full pardon.

Obama's rewriting of the Obamacare law is constitutionally dubious; there is a serious argument that he has not been performing his constitutional duty to faithfully execute the law. But the Constitution is clear in giving the president the “Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment” (Article II, Section 2).

Unless my constitutional interpretation is way off, the president could commute the sentences of all or some of those serving time under sentences that could no longer be imposed under the 2010 law, which Judge Ponsor hails and which President Obama signed.

There is a “darn thing” someone could do about the anomaly Judge Ponsor cites. He sits in the Oval Office, where the buck supposedly stops. Perhaps someone should ask him about it.