California will require police to get a court order before they can search messages, photos and other digital data stored on phones or company servers in the nation's most-populous state.
Civil-liberties advocates called the new law that takes effect Jan. 1 an important advance and said it highlights the need for similar protections at the national level.
The California Electronic Communications Privacy Act was signed by Gov. Jerry Brown on Thursday. It's only the third of its kind in the U.S.
While some states guarantee some of its protections, only Maine and Utah previously had comprehensive laws on the books, noted Hanni Fakhoury, senior staff attorney for the Electronic Frontier Foundation.
"It's an expansive bill and this being California, it covers a lot of people," Fakhoury said of the state with a population of about 39 million. "It's an important thing and a good development."
The digital rights group, along with the American Civil Liberties Union, news organizations and tech companies, worked for the bill's passage. They argued that previous California law dating back to the 1980s was in desperate need of an update given the dramatic changes in the digital world.
But the bill's opponents, including several California police groups, argued that the measure would hamper the ability of law enforcement to investigate child pornographers and others who commit crimes online.