By a 5-4 vote Monday, the court says the Constitution requires that young people serving life sentences must at least be considered for release.

The court ruled in the case of Terrance Graham, who was implicated in armed robberies when he was 16 and 17. Graham, now 22, is in prison in Florida, which holds more than 70 percent of juvenile defendants locked up for life for crimes other than homicide.

''The state has denied him any chance to later demonstrate that he is fit to rejoin society based solely on a nonhomicide crime that he committed while he was a child in the eyes of the law,'' Justice Anthony Kennedy wrote in his majority opinion. ''This the Eighth Amendment does not permit.''

Chief Justice John Roberts agreed with Kennedy and the court's four liberal justices about Graham. But Roberts did not join the majority opinion as it applies to all young offenders who are locked up for crimes other than murder.

Life sentences with no chance of parole are rare and harsh for juveniles tried as adults and convicted of crimes less serious than killing, although roughly three dozen states allow for the possibility of such prison terms. Just over 100 prison inmates in the United States are serving those terms, according to data compiled by opponents of the sentences.

Those inmates are in Florida and seven other states -- California, Delaware, Iowa, Louisiana, Mississippi, Nebraska and South Carolina -- according to a Florida State University study. More than 2,000 other juveniles are serving life without parole for killing someone. Their sentences are not affected by Monday's decision.

Justices Samuel Alito, Antonin Scalia and Clarence Thomas dissented from Monday's ruling.

Thomas criticized the majority for imposing ''its own sense of morality and retributive justice'' on state lawmakers and voters who chose to give state judges the option of life-without-parole sentences.

''I am unwilling to assume that we, as members of this court, are any more capable of making such moral judgments than our fellow citizens,'' Thomas said.

Kennedy, however, said that the high court ruling does not ensure anyone's release. ''What the state must do, however, is give defendants like Graham some meaningful opportunity to obtain release based on demonstrated maturity and rehabilitation,'' Kennedy said.

Kennedy wrote the Supreme Court opinion in 2005 that ruled out the death penalty for people under 18, judging them less responsible than adults.

Monday's decision is an extension of the rationale he used then.

An expert in sentencing law said the outcome is likely to pose challenges to judges and lawyers in cases of young offenders.

For example, are extremely long sentences of 35 years to 40 years that offer no chance at parole before release constitutional?

The court's ''ruling likely will produce challenges for lawyers and lower courts to determine just whether and when other extreme prison terms are constitutionally problematic,'' said Ohio State University law professor Douglas Berman.

In November, the justices heard argument in two cases. The other involved Joe Sullivan, also of Florida, who was sent away for life for raping an elderly woman when he was 13. The court did not issue an opinion in Sullivan's case, but he will benefit from the Graham ruling.