U.S. Attorney General Eric Holder wants to save money on prisons and make the federal justice system fairer — and has proposed doing it by sidestepping Congress. His approach is far from ideal, but the goals are compelling enough to justify it.

The unfairness of criminal sentencing in the United States — and the inequities of mandatory minimum sentences, in particular — is no secret. The system imposes harsher punishments on minorities than on whites and sends nonviolent drug offenders to prison for years. In denying courts the power to take the circumstances of particular crimes into account when weighing sentences, the mandatory minimums renounce a core principle of justice. The situation cries out for remedy.

As Holder said Monday, “Too many Americans go to too many prisons for far too long, and for no truly good law-enforcement reason.” He’s right, and it’s shameful.

He says he has instructed federal prosecutors to employ “locally tailored” guidelines for filing federal charges and, when appropriate, to tweak charges against low-level, nonviolent offenders so that “the accompanying sentences are better suited to their individual conduct.”

In other words, charges will be adjusted so that mandatory minimums won’t always apply. In effect, the discretion in sentencing that Congress took away from the courts is being restored — not to judges but to prosecutors, and not through legislation but through yet another instance of executive action.

The means are unappealing, to put it mildly. It would be far better if lawmakers had acted instead. Congress should already have passed one of the measures proposed occasionally to roll back and preferably abolish mandatory minimums. But it hasn’t, and there seems little immediate prospect that it will. Given this, Holder’s action serves the greater good.