IT IS a tragic fact that children sometimes commit murder. To compound that tragedy, it was, until relatively recently, possible for states to sentence such children to death or to mandate that they spend life in prison without the possibility of parole. Over the past decade and a half, the Supreme Court struck down those laws as the unconstitutional “cruel and unusual punishment” they were. First, it banned the death penalty for juveniles, then mandatory life without parole; finally, the court retroactively granted juveniles who previously had been sentenced to life without parole a chance to argue for new sentences. It’s important to note that the court’s decisions left life without parole for juveniles as a possibility; states just have to consider an alternative first.

On Thursday, however, the court stopped progressing on this moderate and humane road. By a vote of 6 to 3, the justices ruled that states are not obligated to make a legal finding that a juvenile defendant is “permanently incorrigible” before imposing life without parole — even though common sense, and some of the court’s own past words, suggest that’s what locking a child up forever means.

At issue was life-without-parole for a Mississippi 15-year-old, Brett Jones, convicted of stabbing his grandfather to death as they argued in August 2004. As is so often true of juveniles who behave violently, Mr. Jones had himself been the victim of physical abuse in the home of his stepfather, which is why he had moved in with his grandparents. Later, Mississippi’s state courts granted him a chance at a new sentence in light of the Supreme Court’s decisions, but, after a hearing, reimposed life without parole.

In deciding that Mississippi could do so without first determining that Mr. Jones is, essentially, irredeemable, the court was merely sticking to the letter of its previous decisions, which did not call for such a finding, Justice Brett M. Kavanaugh wrote for the majority, composed of the court’s Republican-appointed conservatives. In a blistering dissent, Justice Sonia Sotomayor, joined by two Democratic-appointed liberals, faulted this reasoning as formalistic and accused the majority of, in effect, overruling its previous life-without-parole decisions by easing a state’s burden of showing why a child is one of those rare individuals deserving such a harsh penalty.

We agree, but we hope the dispute between Justice Sotomayor and the majority does not distract from the essential point, which is that no child can be deemed so incorrigible as to be forever denied even the hope of release. Mr. Jones’s own record since incarceration shows why, as Justice Sotomayor noted. He has earned a GED and worked steadily in prison; his grandmother, the widow of his victim, supports an opportunity for parole.

As though to blunt the harsh real-world impact of his ruling, Justice Kavanaugh pointed out that, despite being turned down by the Supreme Court, Mr. Jones still has other avenues of relief, such as clemency from the governor, and that state legislatures may abolish life without parole for juveniles — as 25 states and the District have already done.

For juveniles in the other 25 states, Justice Kavanaugh’s words are cold comfort. At least they clarify that it is up to those legislatures to do justice, because this Supreme Court won’t do it for them. They should. No human being should be pronounced irredeemable at the age of 15.

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