Under a new law effective New Year's Day, California cops can now seize guns from law-abiding Americans without charges and without giving any notice.

And police can keep those firearms for 21 days under the law known as AB 1014.

If family members believe a gun-owning individual is a danger to themselves or someone else, police may acquire a temporary "gun violence" restraining order from a judge, KPCC public radio reported.

California Gov. Jerry Brown signed the law after the 2014 shooting by Elliot Rodger near the University of California, Santa Barbara. Rodger, 22, killed six people and injured 14.

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Before his May 23 shooting spree, Rodger's parents claim they expressed concern about their son's mental state and chilling online diatribes about women.

In his last YouTube video before the shooting, Rodger stated in what appeared to be prepared remarks: "If I had it in my power, I would stop at nothing to reduce every single one of you to mountains of skulls and rivers of blood, and rightfully so."

Police officers visited his apartment three weeks before the spree. Rodger's therapist and mother had told authorities they were concerned about videos the man had posted online. But the officers – who never viewed Rodger's videos – determined he wasn't a threat to himself and, therefore, didn't search his apartment or determine whether he owned guns.

"In the case of the Isla Vista shooter, Elliot Rodger, his mother was noticing that he was becoming more agitated and making these threats of violence, but there was little she could do and little the police could do," said Democratic Assembly member Nancy Skinner of Berkeley, who introduced the bill in 2014 along with Santa Barbara Democrat Das Williams.

As of Friday, California's new law would enable a judge to issue a restraining order against a gun owner based on accounts from family and police.

"The law gives us a vehicle to cause the person to surrender their weapons, to have a time out, if you will," Los Angeles Police Department Chief Michael Moore told KPCC. "It allows further examination of the person's mental state."

A gun owner may challenge the decision three weeks after the firearms are confiscated.

"It's a short duration, and it allows for due process," Moore contends.

The law also requires the California court to notify the Department of Justice when any gun violence restraining order has been issued, renewed, dissolved or terminated.

The state already bans citizens from owning firearms if they have committed violent crimes or were involuntarily committed to mental health facilities. Law-enforcement authorities are also permitted to confiscate guns if a licensed therapist says the owner is a danger to the safety of himself or others.

Moore told KPCC the new firearms restraining order is comparable to a domestic violence restraining order because no conviction is needed.

"It's an opportunity for mental health professionals to provide an analysis of a person's mental state," he said, adding that he doesn't expect "tremendous" use of the new restraining orders by authorities.

Meanwhile, gun-rights advocates are up in arms over the new law.

Sam Paredes, executive director of Gun Owners of California, told the Associated Press: "We don't need another law to solve this problem. We think this just misses the mark and may create a situation where law-abiding gun owners are put in jeopardy."

Charles H. Cunningham, a director with the NRA’s Institute for Legislative Action, wrote, "Without a doubt, AB 1014 is one of the most egregious violations of civil liberties ever introduced in the California Legislature."

And in 2014, Dr. Jason Kissner, associate professor of criminology at California State University, Fresno, called the legislation "the most draconian and flagrantly unconstitutional bill in the state's, and maybe even the nation's, history."

Kissner warned "victims of this proposed law might have no idea they have even been targeted until police show up at the door, conceivably in the middle of the night ..."