ASSOCIATED PRESS The U.S. Supreme Court on Monday offered a window to the more than 2,000 people who were sentenced as teenagers and are now serving life in prison.

The U.S. Supreme Court on Monday ruled that children automatically sentenced to die in prison should get an opportunity to try for a more lenient sentence.

The decision, a 6-to-3 opinion by Justice Anthony Kennedy, made retroactive a 2012 ruling declaring that such sentences for minors -- known as mandatory life imprisonment without the possibility of parole -- are unconstitutional.

"Henry Montgomery has spent each day of the past 46 years knowing he was condemned to die in prison," Kennedy wrote, referencing the Louisiana man at the center of the case. "Per­haps it can be established that, due to exceptional circumstances, this fate was a just and proportionate punishment for the crime he committed as a 17-year-old boy."

Kennedy said that "prisoners like Montgomery must be given the opportunity to show their crime did not reflect irreparable corruption," thus restoring "their hope for some years of life outside prison walls."

The chief question the justices wrestled with in Montgomery v. Louisiana was whether the 2012 decision, Miller v. Alabama, should be extended to every juvenile offender who was sentenced to die in prison without consideration of "youth and its attendant characteristics" -- including factors such as age, upbringing and familial environment.

In answering that question affirmatively, the court reiterated the principle that "children are constitutionally different from adults in their level of culpability" and possess "diminished culpability and greater prospects for reform."

But the Supreme Court didn't outright rule that life imprisonment without parole is never appropriate for youth offenders. Relying on language from prior decisions applying the Eighth Amendment to juvenile punishment, the court instead observed those sentences should still be available, but only for "the rarest of juvenile offenders, those whose crimes reflect permanent incorrigibility."

Still, the ruling could potentially offer a window to the more than 2,000 people who were sentenced as teenagers and are now serving life in prison.

"Allowing those offenders to be considered for parole ensures that juveniles whose crimes reflected only transient immaturity -- and who have since matured -- will not be forced to serve a disproportionate sentence in violation of the Eighth Amendment," the court said.

In dissent, Justice Antonin Scalia -- joined by Justices Samuel Alito and Clarence Thomas -- assailed the court's reasoning and said that extending the 2012 precedent to juvenile sentences that predated it "is just a devious way of eliminating life without parole for juvenile offenders" once and for all.

Scalia then offered this passage.

"And then, in Godfather fashion, the majority makes state legislatures an offer they can’t refuse: Avoid all the utterly impossible nonsense we have prescribed by simply permitting juvenile homicide offenders to be considered for parole," he wrote.

Though it is immediately unclear how the ruling will shake out in the nine or so states that disproportionately sentence juveniles to life imprisonment without the possibility of parole, Kennedy did seem to cabin his opinion by noting that giving this new opportunity to youth offenders will "not impose an onerous burden" on the states.

"The opportunity for release will be afforded to those who demonstrate the truth of Miller’s central intuition -- that children who commit even heinous crimes are capable of change," he wrote.