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A smartphone is sleek, compact and valuable, which makes it a perfect target for a thief. Californian lawmakers want to require cellphone companies to fix that problem.

In the last year, officials in San Francisco and New York have pressured cellphone companies to adopt a so-called “kill switch” that would render a smartphone unusable after it was stolen, which would make it difficult for a thief to sell the device. On Friday, State Senator Mark Leno of California, a Democrat, is expected to introduce legislation requiring all smartphones and tablets sold in the state to include this kind of feature.

The bill, which is sponsored by George Gascón, San Francisco’s district attorney, would require phones sold in California on or after Jan. 1, 2015, to include the antitheft solution. Companies that sold phones without kill switches would be subject to fines of up to $2,500 for each device sold.

If passed, the legislation would most likely push smartphone makers to add kill switches in all their devices in the country, because it would be inefficient for manufacturers to make cellphones meant to be sold only in California.

“With robberies of smartphones reaching an all-time high, California cannot continue to stand by when a solution to the problem is readily available,” Senator Leno said in a statement. “Today we are officially stepping in and requiring the cellphone industry to take the necessary steps to curb violent smartphone thefts and protect the safety of the very consumers they rely upon to support their businesses.”

In 2012, smartphone thefts reached highs in several metropolitan cities, and they rose again last year. In San Francisco, 2,400 cellphones were stolen last year, a 23 percent rise from 2012, according to the San Francisco police. Phone thefts also grew in New York and Washington, D.C., last year, according to statistics from the police in those cities.

Senator Leno’s legislation will almost certainly face resistance from CTIA, the industry trade group that represents the cellphone carriers like AT&T, Verizon Wireless and T-Mobile US. Last year, CTIA said in a filing to the Federal Communications Commission that “a kill switch isn’t the answer.”

CTIA said that a kill switch would pose risks, because hackers who took control of the feature could disable phones for customers, including the phones used by officials in the Department of Defense and in law enforcement.

The group also argues that if a phone were deactivated and the owner later retrieved it, the owner could not reactivate it. But in the case of Apple’s new antitheft feature, Activation Lock, a customer can disable a phone that has been lost as well as reactivate it with the correct user name and password after the device has been found.

Michael Altschul, senior vice president and general counsel for CTIA, said the carriers moved quickly to work with government and law enforcement officials to address cellphone theft. He said the group had helped create a nationwide database for deactivating cellphones that have been reported stolen.

Several law enforcement officials, however, have said that the database is not enough to solve the problem. Many stolen phones end up overseas, out of the blacklist’s reach.

In October, New York State Senator Jeffrey D. Klein, a Bronx Democrat, introduced a bill to go after the sellers of stolen phones by making it illegal for any business in the state to buy or sell a used smartphone without proof of legitimate ownership. The bill is sitting in a Senate committee.

Mr. Klein’s bill would require any business buying a used smartphone to collect a receipt of ownership, including serial numbers for the device. If a business cannot show that it bought used cellphones with proper documentation, the business could face fines or its owner could face imprisonment.