Effective today, smartphones sold in California must now come with anti-theft technology that can remotely disable the devices — a “kill switch.”

The mandate comes from 2014 state legislation sponsored by State Sen. Mark Leno, D-San Francisco, and supported by San Francisco District Attorney George Gascon. The bill’s aim is to reduce the incentive to steal smartphones and use or resell them.

Some — not all — smartphone manufacturers initially opposed the legislation, citing concerns about a state regulating the specifications of a product that’s sold nationally. Sentiment seems to have shifted during the past year.

On Wednesday, CTIA – The Wireless Association lauded the industry’s support and fulfillment of a “Smartphone Anti-Theft Voluntary Commitment” for smartphones sold to U.S. consumers. More than a dozen companies — such as Apple, Google, Samsung, T-Mobile and Verizon  — are participating. For example, Apple’s “Activation Lock” was added in fall 2013; an Android kill switch followed in early 2014.

The technology includes capabilities that lock or wipe missing devices while still enabling 911 calls when the phone is locked, according to CTIA.

USA Today reported earlier this year that since kill switches have been added, smartphone theft has dropped 40 percent in London, 22 percent in San Francisco and 16 percent in New York, according to the New York Attorney General’s Office, one of the organizers of the Secure Our Smartphones (SOS) initiative.

Consumer Reports estimated 1.6 million Americans were victims of smartphone theft in 2012.

The new California law says smartphone owners must be able to disable the kill switch if they choose. A “knowing retail sale” of a smartphone in violation of the new law would incur penalties between $500 and $2,500 for each instance.

This story was originally published my Techwire