California Gov. Jerry Brown signed into law today a measure making the state America’s first “sanctuary state,” enshrining statewide protections to shield undocumented people which had previously only existed at the local level.

“These are uncertain times for undocumented Californians and their families, and this bill strikes a balance that will protect public safety, while bringing a measure of comfort to those families who are now living in fear every day,” Brown said in statement.

The law, which was dubbed the California Values Act in the state Senate, explicitly prohibits local officials, including school employees and security workers, from using their resources to help federal immigration officials round up undocumented people. It also establishes schools, public libraries, health facilities, and courthouses as safe zones where people cannot be arrested because they are undocumented—protections that have been almost completely eliminated under Donald Trump.

With some exceptions, the law also bars state agencies from transferring undocumented people to ICE unless a judge issues a warrant or the person has certain prior convictions. Agencies also won’t be allowed to give ICE a person’s release date from jail, according the Los Angeles Times. Those provisions are almost certain to kick off a legal firestorm with the Justice Department.

Attorney General Jeff Sessions was already waging war on sanctuary cities, including San Francisco. Sessions had threatened to withhold a portion of federal funding from cities that refuse to hand over undocumented people to ICE with an order that was almost immediately halted by a federal judge, and he has called California’s newest law “unconscionable” and a threat to public safety.


Even before Brown signed the measure, the bill’s author, California Senator Kevin de León, of Los Angeles, had already said state leaders were prepared to defend the measure in court.

Brown’s signing of the bill, which the state legislature approved on the last day of its 2017 session in September, coincides with today’s deadline for DACA recipients to apply for a final extension before the program formally ends in March.