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 iniquities 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: The wrongs of the current regime are just too great to ignore.

Holder is not alone in his critique. “I can accept neither the necessity nor the wisdom of federal mandatory minimum sentences,” U.S. Supreme Court Justice Anthony Kennedy said in a 2003 speech. “In too many cases, mandatory minimum sentences are unwise or unjust.” In a ruling in June, the high court slightly curtailed the nation’s sentencing rules, but too much injustice remains.

Too much crippling cost, as well. The federal prison population has grown almost 800 percent since 1980, to more than 219,000. (The U.S. population grew by one-third over the same period.) Federal prisons are almost 40 percent over capacity.

Altogether, more than 1.5 million people were incarcerated in 2012 in local, state or federal institutions. The Justice Department says the bill was $80 billion in 2010. The cost in needlessly destroyed lives is frightening to contemplate.

Where Congress has failed to act, states have been reforming. From New York to California, South Dakota to Texas, prison reforms are saving public money while treating offenders more fairly and giving some a better shot at redemption. From 2001 to 2011, according to the Pew Charitable Trusts’s Public Safety Performance Project, 16 states reduced both imprisonment and crime rates.

It’s never too late for Congress to clean up a mess of its own making. In the Senate, Republicans Mike Lee and Rand Paul and Democrats Dick Durbin and Patrick Leahy are backing different bipartisan versions of legislation to give federal judges greater discretion in sentencing. The rest of the Senate should join their efforts.

Sentencing reform is a cause on which liberals and conservatives can and should unite. Meanwhile, Holder has acted, and he was right not to wait.

Editorial by Bloomberg View