About two years ago, the Florida Supreme Court decided that juvenile offenders serving sentences so lengthy that they amount to life in prison must have their cases reconsidered.

The ruling applied even to juveniles who at some point would be eligible for parole, opening up the possibility of new and shorter sentences for hundreds of inmates.

Since then, some long-timers have been released. Many others await re-sentencing.

But now, they might not get a chance after all.

In recent weeks, the high court has overruled its earlier decision, effectively barring parole-eligible inmates from being re-sentenced.

The abrupt change could mean many of those who have already done decades in prison for their juvenile crimes will remain there for good.

"It's really concerning for the court to change its mind after such a short period of time," said Roseanne Eckert, the coordinating attorney for the Juvenile Resentencing and Review Project at Florida International University College of Law. "We have more than 200 people that were basically told, 'Too bad, you missed your chance.'"

Why the change? To understand, it helps to know a bit of recent legal history.

In 2010 and 2012, the U.S. Supreme Court held that it was unconstitutional to sentence juvenile defendants to life in prison without parole. The cases, Graham vs. Florida and Miller vs. Alabama, were rooted in scientific research showing that juvenile brains are different — and that teenagers are less capable of understanding consequences.

Florida law was changed to require that judges conduct individual sentencing hearings for each juvenile and consider specific factors including the defendant's age, maturity and educational background.

Then, in 2016, came the case of Angelo Atwell. He's serving a life sentence for the 1990 murder of a Broward County high school economics teacher, a crime he committed when he was 16.

Now in his 40s, Atwell is parole eligible. But the Commission on Offender Review said the earliest he could be considered for release is 2130, far beyond his life expectancy.

His sentence, the Florida Supreme Court said, was virtually indistinguishable from life without parole.

"We conclude that Florida's existing parole system ... does not provide for individualized consideration of Atwell's juvenile status," Justice Barbara Pariente wrote for the court's 4-3 majority.

Florida abolished parole for most offenses in 1983. It was abolished for good in 1994. Parole still applies to people sentenced before that, who number more than 4,000.

The court's ruling meant that parole-eligible inmates who committed crimes as juveniles could ask judges to re-sentence them.

About 60 people have been released since then, Eckert said. A handful got new life sentences.

Hundreds more were in the process of seeking new sentences when the high court reversed itself this year in the case of Budry Michel.

Michel was 16 in 1991 when he was charged with a spate of crimes including first-degree murder. He, too, is parole eligible.

Justice Ricky Polston said there is no evidence that the state's parole system fails to provide a "meaningful opportunity for release." Polston cited a recent federal case upholding the constitutionality of Virginia's prison geriatric release program.

The makeup of the court has changed since the Atwell decision. Justice E.C. Perry, who was in the majority in that case, retired in 2016. He was replaced by Justice Alan Lawson, who concurred with Polston in the Budry case.

The Budry decision became final this month. On Nov. 8, the court cited it in upholding the sentence of Arthur O'Derrell Franklin, who is serving a 1,000-year sentence for a series of brutal rapes he committed at age 17 in 1983. His presumptive parole release date is in 2352.

"I think that is an indication the court is going to be far more conservative and far less willing to give kids, at least, relief for their incarceration," said Stephen Harper, who leads the Juvenile Resentencing and Review Project at Florida International University.

Critics say the process doesn't come close to an individual re-sentencing hearing like the one required under the new juvenile sentencing laws. And it's rare that anyone gets released on parole.

"You don't even really get a hearing," said Teri Sopp, a Jacksonville assistant public defender, who is working on an analysis of parole denials in the hope of litigating the issue. "You get an administrative review that last 10 minutes. And that's 10 minutes between the victim and the defendant and the prosecutor.

"It's the furthest thing from a meaningful review that could possibly exist."

Contact Dan Sullivan at dsullivan@tampabay.com or (813) 226-3386. Follow @TimesDan.