SACRAMENTO — Ninety percent of California sex offenders will no longer be required to register with law enforcement for life under a bill that Gov. Jerry Brown signed Friday.

The change is one of several sweeping alterations to the state’s 70-year-old registry contained in SB384 by Sen. Scott Wiener, D-San Francisco.

The bill allows most sex offenders to petition beginning in 2021 to be removed from both the public and the police registries 10 to 20 years after they are released from prison, as long as they have not committed another serious or violent felony or sex crime.

Brown had previously indicated he would sign the reform, which for years stalled amid pushback from reluctant lawmakers who did not want to be seen as soft on crime. The bill was pushed by law enforcement agencies, that argued that California’s sex offender registry is so large that officers and the public can’t determine who is at high risk for reoffending. The registry has 100,000 sex offenders — meaning 1 in 400 Californians is on it.

California is one of four states to require lifetime registration.

“With this reform, our law enforcement agencies will be able to better protect people from violent sex offenders rather than wasting resources tracking low-level offenders who pose little or no risk of repeat offense,” Wiener said in a statement. “Our sex offender registry is a tool used to prevent and investigate crimes, and these changes will make it a better and more effective tool for keeping our communities safe.”

The state’s registry will have now have three tiers, with the first tier allowing people convicted of crimes like misdemeanor sexual battery, misdemeanor possession of child pornography and indecent exposure to petition to be removed from the registry after 10 years. Tier one has the largest number of sex offenders, with up to 65,000 people potentially falling into that category.

Those offenders would not all come off the registry at once since a portion of those people would not have finished waiting the mandatory minimum of 10 years on the registry after their release from prison.

The next tier includes people convicted of lewd and lascivious acts with a minor, oral copulation with a minor under 14 years old and non-forced sodomy with a minor under 14 years old. The second tier, which requires sex offenders to register for a minimum of 20 years, has potentially 24,000 people.

Crimes like rape, sex crimes against children 10 and younger, repeated sex crimes and sex trafficking minors, put a sex offender in a third tier that requires them to be on registry for life. That tier has an estimated 8,200 people.

LGBTQ groups like Equality California supported the bill, saying the changes will help gay and lesbian people who were targeted by police for crimes like consensual sex among adults in a park.

“Gov. Brown’s signature will restore livelihoods and help restore the registry as a tool for investigating those who pose a real danger to society,” said Rick Zbur, executive director of Equality California.

Under current law, when a person is required by a judge to register as a sex offender, there are few ways to have their name removed from the registry, regardless of the underlying offense. That’s resulted in a registry that includes 650 sex offenders whose last convictions were in the 1940s and 1950s, according to the Sex Offender Management Board. Another 3,000 were last convicted of a sex crime in the 1960s and 1970s.

Supporters of the bill, including scholars and victim advocates, argued that research shows that the longer people are crime-free, the less likely they are to reoffend, thus keeping sex offenders on the registry for decades does not reduce crime.

Local law enforcement agencies estimated that they spend two-thirds of the money intended for supervising sex offenders on paperwork for low-risk offenders. That money, Alameda County District Attorney Nancy O’Malley argued, would be better spent monitoring higher-risk offenders.

Melody Gutierrez is a San Francisco Chronicle staff writer. Email: mgutierrez@sfchronicle.com Twitter: @MelodyGutierrez