(Kiyoshi Ota/Bloomberg)

TOO MANY Americans have been there: confronted on sidewalks, reaching for their wallets, only to learn that the thieves are most interested in their smartphones. Spending hundreds to replace these indispensable tools is bad enough. Worrying that criminals might have access to sensitive data is worse. Then there is the grating realization that some unscrupulous phone-buyer is walking around with your smartphone, purchased shadily with no questions asked.

California is now requiring phone makers to adopt technology that could end this scourge. The rest of the country should, too.

Smartphone theft nearly doubled last year, when 3.1 million were stolen, according to Consumer Reports. Major police departments report that as many as 40 percent of robberies involve small electronics. The attraction for petty thieves is strong because sophisticated devices can be wiped and resold, often abroad.

On Monday, California Gov. Jerry Brown (D) signed a bill that would require all smartphones sold in the state to come with a “kill switch,” starting next July. Victims could send a signal to their stolen phones that would wipe the data and prevent others from easily using the unit. Killed smartphones could be restored, but only by entering a password. This wouldn’t eliminate the possible usefulness of stolen smartphones to criminals with time and technical savvy, but it would take a lot more effort for crooks to profit from wide-scale theft.

Seems obvious to us, as it does to District Police Chief Cathy L. Lanier and a variety of law enforcement officials across the country. But the wireless industry has pressed back. Malicious hackers might find ways to flip kill switches without owners’ permission, they warn. Major smartphone players such as Apple and Google are getting the message and offering kill-switch-like features to their customers. Police are already reporting drops in the theft of Apple products. If that’s so, why not make kill switches standard?

California’s approach is particularly strong because it requires that the kill switch be primed and ready for activation when people buy their smartphones rather than relying on phone owners to set it up. That mandate will maximize the theft-deterrent value of the policy and save technologically ill-adept phone users a lot of trouble.

The industry also complains that it does not want to be required to comply with a patchwork of state security standards. We have an easy answer to that problem: Put in place a federal rule mirroring California’s that would apply everywhere.