SACRAMENTO — California will expand its landmark gun violence restraining order law, allowing co-workers and employers to ask a judge to take away someone’s firearms and extending the maximum length of the bans.

Gov. Gavin Newsom signed four bills Friday to bolster the restraining order program, which now allows police, immediate family members and roommates to request that a judge temporarily confiscate firearms and ammunition from people they believe pose a danger to themselves or others.

Following a signing ceremony at his Capitol office with lawmakers and advocates, Newsom said the measures would continue California’s success in reducing its murder and suicide rates faster than the rest of the country.

“This is another tool in the tool kit from those that know individuals the most,” he said. “What’s inevitable is you’re going to see these expansions in other parts of the country, and I think this will also expand the debate in Congress.”

Supporters say the law is one of the most effective tools the state has to prevent gun violence, enabling authorities to intervene when they see “red flag” behavior. But it was lightly used in the first three years after it took effect in 2016, particularly compared with other states that have similar programs.

AB61 by Assemblyman Phil Ting, D-San Francisco, will add employers, co-workers and school employees to the list of people who can ask a judge for the restraining order. His AB1493 will create a way for someone subject to an order to voluntarily relinquish their gun ownership.

“With so many mass shootings at workplaces and schools, it only makes sense that we expand our gun violence restraining orders” to workplaces and schools, Ting said in an interview.

Under AB12 by Assemblywoman Jacqui Irwin, D-Thousand Oaks (Ventura County), judges will now be able to issue gun violence restraining orders and renewals for up to five years, instead of the current one-year limit. Defendants will still be able to petition a court to end an order early.

Irwin said in an interview that longer orders would be useful for people with several mental health conditions and other situations that a judge would not expect to quickly improve.

“This is really to alleviate the burden on the court system and alleviate the burden on families,” she said.

California adopted its gun violence restraining order law following the 2014 killings of six people in Isla Vista, near UC Santa Barbara. The killer had posted threatening videos online, prompting his parents to ask authorities to check on him. Officers did so, but did not search his apartment for weapons.

Despite slow adoption of the restraining orders statewide, some law enforcement agencies have made them a regular part of their response to volatile situations involving workplace disputes, domestic violence and gun owners struggling with drug abuse and trauma.

In a study released in August, UC Davis researchers found at least 21 cases in which a gun violence restraining order was used to intervene before a potential mass shooting. None of the subjects of the orders committed crimes involving gun violence after their weapons were taken away, the study said.

Irwin’s AB339, which Newsom signed Friday, will require law enforcement agencies to develop standards for using gun violence restraining orders.

Gun rights advocates argue that the restraining orders are unconstitutional, in part because a court can seize defendants’ weapons for up to three weeks before the gun owner has a chance to appear before a judge. Civil liberties groups raised additional concerns that allowing more people to seek orders could open the process to abuse, because those people may lack the relationships or skills to properly assess whether a gun owner is dangerous.

Then-Gov. Jerry Brown twice vetoed similar measures carried by Ting. In 2018, he wrote that “law enforcement professionals and those closest to a family member are best situated to make these especially consequential decisions.”

But continuing mass shootings, such as one this summer at the Gilroy Garlic Festival that left three victims dead, have stirred urgency in the Legislature and with Newsom to find additional ways to crack down on gun violence.

Newsom signed 11 other gun control measures, including:

• AB164 by Assemblywoman Sabrina Cervantes, D-Riverside, which authorizes California law enforcement officers to remove weapons from people who are not allowed to own guns because of a restraining order in another state.

• AB879 by Assemblyman Mike Gipson, D-Carson (Los Angeles County), which requires that parts that could be used to build a gun at home be sold through a licensed manufacturer after a background check, starting in July 2024.

• SB61 by Sen. Anthony Portantino, D-La Cañada Flintridge (Los Angeles County), which limits gun buyers to one semiautomatic center-fire rifle per month and forbids Californians under age 21 from purchasing them.

• SB376 by Portantino, which requires that guns won at charity auctions or raffles be transferred through a licensed dealer and that the recipients undergo a waiting period.

• AB645 by Irwin, which adds a suicide prevention hot line number to the warning label on gun packaging and requires the written test for a handgun safety certificate to cover suicide.

• AB1297 by Assemblyman Kevin McCarty, D-Sacramento, which eliminates the $100 limit for concealed-carry license fees and requires counties to charge what it costs to pay for administering the program.

• AB 521 by Assemblyman Marc Berman, D-Palo Alto, which directs the University of California Firearm Violence Research Center to develop education and training programs for medical and mental health providers on preventing gun injuries.

Alexei Koseff is a San Francisco Chronicle staff writer. Email: alexei.koseff@sfchronicle.com Twitter: @akoseff