The new ruling could worsen existing racial disparities in states that condemn teens to die in prison.

For years, the Supreme Court sent a consistent message about kids who commit the most serious crimes: They’re still kids. Their bad decisions are often a product of abusive upbringings and still-developing brains. So they can’t be executed. And they can’t get life without parole unless they kill someone — and even then, “all but the rarest of children” deserve a chance at release.

The decisions ushered in a major change: Thirty-one states and the District of Columbia have now either banned life without parole for juveniles altogether or have no one serving the sentence. Some states have gone even further, curtailing long prison terms for teens, and providing special protections in other contexts, like parole board hearings.

This month, however, the momentum seemed to change direction.

First, the Supreme Court’s new conservative majority issued a ruling that curtailed the impact of Miller v. Alabama, the court’s 2012 decision restricting life without parole for teenagers. Then, Evan Miller, the man whose name became synonymous with more than a thousand juvenile lifers having a chance to go home, was himself resentenced to life in prison without the possibility of parole.

“It feels like a one-two punch,” said Ashley Nellis, a research analyst with the Sentencing Project, a think tank that advocates against life sentences. “We’re in a different era.”

Justice Sonia Sotomayor, in a dissent, said the recent ruling “guts” Miller v. Alabama. But the reality may be more complicated, juvenile justice experts say. Life without parole sentences for youth are concentrated in a minority of states and counties, and most states will likely continue to restrict them. But in states where judges do sentence teens to life without parole, existing disparities of race and geography will widen, experts predict.