Smartphones are smart enough these days to do almost anything. So why can’t they make themselves useless to thieves? That’s the idea behind a new bill in California.

Introduced in the legislature Friday by State Senator Mark Leno, the proposed law will require a kill switch of some kind on all such devices sold in the state.

The exact technology to be used is not specified, but the result must be a completely useless phone if deactivated by its owner. An owner could opt out of the kill switch if they so chose. Any company that sold a switchless phone could receive a fine of up to $2,500 for each one.

Given California’s size and bellwether position, such legislation would likely lead to kill switches on all smartphones sold in the U.S.. The bill has garnered support from major local officials, including the mayor and police chief in Los Angeles and the district attorney for San Francisco.

Leno noted in a statement that robberies of smartphones have hit a record high. In San Francisco, half of all robberies involve a smartphone. Nationally, it’s one in three, according to the Federal Communications Commission. A stolen iPhone in San Francisco can go for as much as $650 in cash, depending on the model.

The idea, according to U.S. Senator Charles Schumer of New York, who supports related national legislation, is to “make a stolen cellphone as worthless as an empty wallet.”

Parallel Effort in New York

A parallel effort has been underway by local New York officials. New York State Senator Jeffrey Klein and Assemblyman Jeff Dinowitz introduced a bill in October that would make it illegal to buy a phone unless it came with documented ownership papers. That bill, which exempts sales between individuals, is still under consideration by a committee in the State Senate.

Klein and Dinowitz’s home districts include part of the Bronx, where a 26-year-old Korean immigrant was shot and killed in 2012 for his iPhone.

The CTIA wireless industry trade group opposes a kill switch, arguing that hackers could employ it against the owner. The organization also has said that the central database it developed with the FCC and police departments allows wireless providers to disable and block a stolen device.

Some police officials have criticized the database approach, because of its reliance on easy-to-modify phone identifiers and because some stolen phones are sent out of the U.S., beyond the database’s reach.

Phone makers and carriers have been criticized for not devoting enough attention to this matter. After all, a lost or stolen phone means the victim has to buy a new phone, and prevention against theft is why carriers sell insurance policies.

San Francisco District Attorney George Gascon and New York Attorney General Eric Schneiderman have said that smartphone makers have until June to come up with their own industry solutions.