More than forty years after the U. S. government launched the modern drug war, its highest-ranking prosecutor has tacitly admitted that it is a legal and moral failure:

In a major shift in criminal justice policy, the Obama administration moved on Monday to ease overcrowding in federal prisons by ordering prosecutors to omit listing quantities of illegal substances in indictments for low-level drug cases, sidestepping federal laws that impose strict mandatory minimum sentences for drug-related offenses.

Attorney General Eric H. Holder Jr., in a speech at the American Bar Association’s annual meeting in San Francisco on Monday, announced the new policy as one of several steps intended to curb soaring taxpayer spending on prisons and help correct what he regards as unfairness in the justice system, according to his prepared remarks.

Saying that “too many Americans go to too many prisons for far too long and for no good law enforcement reason,” Mr. Holder justified his policy push in both moral and economic terms.

At the risk of giving Holder too much credit, it is encouraging that he is not viewing his end-run around mandatory minimums for drug offenses in purely utilitarian terms: he recognizes the injustice of current laws which have contributed to the world’s highest incarceration rate. But it’s worth noting that these reforms follow the lead of several conservative Southern states, which have turned to treatment, diversionary programs, and early release for non-violent offenders as a way to relieve prison overcrowding. Texas, far and away the nation’s leader in executions, has experienced a steady drop in its prison population after adopting sentencing reforms aimed at rehabilitation instead of imprisonment, and is actually closing prisons it no longer needs.

Whether Holder’s proposed reforms will have a similar effect on federal prison populations remains to be seen. One caveat is that this does not represent any long-term reform of the actual mandatory minimum sentencing guidelines. Holder is simply using his prosecutorial discretion to not issue indictments that could lead to lengthy prison terms. The laws are still on the books and only Congress can change or repeal them. Should Obama or his successor appoint a more enthusiastic drug warrior, even this modest progress could be reversed. It’s also unclear who will qualify as a “low-level” drug offender. Your friendly neighborhood pot dealer may get lucky with this policy change, but it’s unlikely that purveyors of harder stuff will be unrelated “to large-scale organizations, gangs, or cartels” in the feds’ view.

But it’s a start. If President Obama wants to leverage the political capital he’ll gain from these reforms, he could take even more dramatic action to reduce prison populations by using his clemency powers to reduce the sentences of minor drug offenders. But as he has demonstrated throughout his time in office, Obama’s mercy for incarcerated Americans is quite limited.