Gov. Arnold Schwarzenegger signed legislation Thursday to put some sex offenders in prison for life at a bittersweet ceremony for family and friends of a 17-year-girl who was killed after being abducted while running less than seven months ago.

Chelsea's Law is named for Chelsea King, who was killed by 31-year-old convicted child molester John Gardner. He was sentenced to life in prison in May after pleading guilty to murdering Chelsea and 14-year-old Amber Dubois.

"Because of Chelsea, California's children will be safer. Because of Chelsea, this never has to happen again," said Schwarzenegger, an early backer of the legislation.

The ceremony began under a light drizzle then gave way to sunshine at an outdoor theater in Balboa Park, where Chelsea played French horn for the San Diego Youth Symphony. Many of the 200 people in the audience carried sunflowers, her favorite flower.

Brent and Kelly King, who traveled from their new home in suburban Chicago, thanked lawmakers for speeding the bill through the Legislature with overwhelming bipartisan support.

Brent King said he was initially skeptical about the bill's prospects and had been preparing to sponsor a ballot initiative.

"No offense, guys," he said, providing a light moment as he turned to Democratic Assembly Speaker John Perez and other lawmakers in attendance.

Kelly King said the lawmakers were an example for young people.

"You've shown them what is good, what is right and what is sound decision-making," she said.

The Kings, in an interview, said they plan to promote similar legislation in other states and have tentatively targeted Texas, Florida, Colorado and Ohio, the scenes of high-profile child abductions. They have not settled on a timetable.

The Kings have not been considering their new home state of Illinois for legislation because they want to shield their 14-year-old son Tyler from the spotlight. The avid baseball player has recently shown renewed interest in the game.

"We've seen Tyler sort of come back into his own," Kelly King said. "He walks in the door after school and he has a smile on his face."

The Kings plan to use their nonprofit foundation, Chelsea's Light, to promote peer counseling programs — one of Chelsea's favorite causes — and to offer scholarships for college and other programs.

Chelsea's Law allows life without parole sentences for adult predators who kidnap, drug, bind, torture or use a weapon while committing a sex crime against a child. Life terms could be ordered for first-time and repeat offenders.

It also increases other penalties for child molesters, including requiring lifetime parole with GPS tracking for people convicted of forcible sex crimes against children under 14. Previous law permitted lifetime GPS monitoring, but most tracking ended when offenders leave parole.

Assemblyman Nathan Fletcher, the San Diego Republican who spearheaded the Chelsea's Law legislation, said in an interview it would have resulted in a longer prison sentence, possibly life, and longer parole for Gardner in 2000 for molesting a 13-year-old neighbor.

Gardner served five years of a six-year sentence and repeatedly violated parole.

Supporters came to the ceremony wearing T-shirts with one of Chelsea's favorite quotations, "They can because they think they can," from the Roman poet Virgil.

"I don't think this is the end," said Sunil Homes, 18, a former classmate of Chelsea at Poway High School in suburban San Diego. "This is more like a milestone. The next milestones are other states and hopefully the nation."

Danielle Stiritz, 32, came to the ceremony with her two young daughters. She collected signatures earlier this year to urge lawmakers to support the legislation.

"It's really neat to see the positive that can stem from a tragedy," she said.