Richard Nieva/CNET

California on Monday became the first state to require that antitheft security features come enabled by default for every smartphone sold in the state.

Gov. Jerry Brown signed the so-called "kill switch" bill -- introduced in February by State Sen. Mark Leno and sponsored by San Francisco District Attorney George Gascon -- on Monday, after it passed the state legislature earlier this month. A smartphone kill switch enables an owner to lock down a phone if it is stolen, rendering it inoperable. A spokesperson from Brown's office said the governor was not available for comment.

In May, Minnesota became the first state to pass a kill switch bill, but that law does not require the feature come turned on as the default setting, when a consumer initially sets up his or her new smartphone -- a distinction supporters of the California bill deem very important.

"Opt-in does not end the problem. Because it will not be ubiquitous," said Leno on the Senate floor in April, the first time the bill was presented. The idea is that if thieves expect the software to be enabled on all phones, they won't bother stealing them in the first place. After a heated debate, the legislation narrowly failed its first go-around but passed after a second try two weeks later.

"California has just put smartphone thieves on notice," Leno said Monday, in a statement.

The law aims to address what government officials have called an "epidemic." One in 10 smartphone owners in the US has had a phone stolen, according to the mobile security firm Lookout. In 2013, more than 3 million Americans were the victims of smartphone theft -- nearly twice as many as the year before, according to Consumer Reports. In San Francisco, which Leno represents and over which Gascon presides, thefts of mobile devices made up 65 percent of robberies in 2013. In Oakland, it was 75 percent.

"Seldom can a public safety crisis be addressed by a technological solution, but today wireless consumers everywhere can breathe a sigh of relief," said Gascon, in a statement.

The law will apply to smartphones -- not tablets or other devices -- sold in the state after July 1, 2015. There will be a penalty of $500 to $2,500 for the "knowing retail sale" of every phone not in compliance.

The bill has received some pushback from the wireless industry, which believes a kill switch could be exploited by hackers. But supporters of the law have questioned the motivations of mobile carriers, which have lucrative deals with insurance partners.

The CITA, a trade organization representing the wireless industry, derided Brown's decision. "Today's action was unnecessary given the breadth of action the industry has taken," Jaime Hastings, vice president of external and state affairs for the CTIA, said in a statement.

"State by state technology mandates, such as this one, stifle those benefits and are detrimental to wireless consumers."

The law requires the security software to come enabled by default, but other than that, not much will change for most smartphone holders. Apple and Samsung, the No. 1 and 2 smartphone makers in the world, already have antitheft software available on their phones.

Last September, Apple added "activation lock," a feature that makes it harder for someone to use a stolen iPhone. The program requires a user's Apple ID and password before they can turn off the phone's location tracking or reactivate a locked phone. In April, Samsung, maker of the popular Galaxy smartphone line, launched "reactivation lock," which prevents a locked phone from being made operable again, even through a factory reset.