California Gov. Jerry Brown recently signed SB 9, a bill that has been introduced several times over the last few years, but had never made it to the governor's desk.
The bill becomes law at an interesting time. Recent cases in the U.S. and California supreme courts have called for lighter sentences for juveniles.
In signing the bill, the governor agreed that children are fundamentally less culpable - and are more likely to change - than adult offenders. Under the new law, offenders locked up for life as juveniles will be able to petition the court for parole hearings.
The retroactive part of the law has upset some victims' rights activists.
LaWanda Hawkins is the founder of Justice for Murdered Children.
She said it's hard for survivors to stir up old memories of cases that were supposed to be over.
"We went through the judicial system, we went through the trials," Hawkins said. "The jurors have already decided, the judge made a decision. We expect our governor to hold up the law, not to be changing it."
Abel Habtegeorgis, with the Ella Baker Center for Human Rights, which advocates for young people behind bars, said he feels the pain of people who've suffered great losses.
But he said it is time for California to scale back what he calls harsh sentencing laws.
Habtegeorgis said the new law represents a small step in that direction.
"We're finally having these conversations, even though it's 2012, we probably should have had this conversation a long time ago," Habtegeoris said. "And now hopefully we can do effective criminal justice reform sooner rather than later."
The law is expected to affect about 300 current inmates.
"It's the deep end of the pool," agreed University of California, Berkeley Law Professor Franklin Zimring, an expert on juvenile justice. "We offer such long sentences to children in the juvenile system, putting them in the [adult] criminal system is just adding insult."