LOS ANGELES, California — California will be the first state to ban most law enforcement, including federal immigration agents, from covering their faces while conducting official business under a bill signed by Gov. Gavin Newsom on Saturday.

The ban is California’s direct response to a recent series of immigration raids in Los Angeles where federal agents wore masks while making mass arrests. The raids prompted a dayslong protest across the city and led President Donald Trump to deploy National Guard troops and Marines to the area.

But it’s unclear how – or whether – the state can enforce the ban on the federal agents who have been carrying out those raids. A homeland security official called the legislation “despicable” in a statement this week, adding that the ban would only put officers in danger.

Assemblymember Al Muratsuchi, D-Torrance, said at a press conference in Los Angeles that “students cannot learn if they live in fear of being deported. The California Save Haven Schools Act is a clear message to Donald Trump: ‘keep Ice out of our schools.'”

The Department of Homeland Security said it had sent letters Friday to the attorneys general in California, Illinois and New York reinforcing previous instructions that the Democrat-led states honor detainers from the U.S. Immigration and Customs Enforcement for “criminal illegal aliens within their jurisdictions.” DHS said in a statement Saturday that if the states failed to comply, it would pursue “all appropriate measures to end their inadvisable and irresponsible obstruction.”

Messages seeking comment from the DHS and ICE after the law was signed were not immediately returned.

Newsom, a Democrat who has railed on federal agents’ use of masks during official business, said the measure will help California push back on federal overreach. He signed the bill in Los Angeles, flanked by state lawmakers and immigrant community members.

The new law prohibits neck gators, ski masks and other facial coverings for local and federal officers, including immigration enforcement agents, while they conduct official business. It makes exceptions for undercover agents, medical masks such as N95 respirators or tactical gear. It doesn’t apply to state police.

Trump administration officials have consistently defended the practice, saying that immigration agents have faced strident and increasing harassment in public and online as they have gone about their enforcement in service of Trump’s drive toward mass deportation, and hiding their identities is for their and their families’ safety.

Federal agents are already instructed to identify themselves and wear vests with ICE or Homeland Security markers during operations, Homeland Security Assistant Secretary Tricia McLaughlin said in a statement this week.

“The men and women at CBP, ICE, and all of our federal law enforcement agencies put their lives on the line every day to arrest violent criminal illegal aliens to protect and defend the lives of American citizens,” she said.

Democrats in Congress and lawmakers in several states, including Tennessee, Michigan, Illinois, New York, Massachusetts, and Pennsylvania, have also introduced similar proposals calling for mask bans for law enforcement officers.

Proponents said the mask ban is especially needed after the Supreme Court earlier this month ruled that the federal administration can resume the sweeping immigration operations in Los Angeles. The new law aims to boost public trust in law enforcement and stop people from impersonating officers to commit crimes, supporters said.

Constitutional law expert Erwin Chemerinsky at the University of California, Berkeley, also defended the legislation. Federal employees still have to follow general state rules “unless doing so would significantly interfere with the performance of their duties. For example, while on the job, federal employees must stop at red lights,” he wrote in an opinion piece for the Sacramento Bee.

The increase in high-profile immigration enforcement was already contentious between those opposed to the actions of Trump’s administration and those in support of them. The sight of masked agents carrying it out is creating a whole new level of conflict.

The mask ban is among a number of measures approved by the Democratic-controlled Legislature in response to Trump’s immigration policies of mass deportation. Newsom on Saturday also signed legislation to prevent immigration agents from entering schools and health care facilities without a valid warrant or a judicial order and to require schools to notify parents and teachers when immigration agents are on campus.

It’s part of state lawmakers’ efforts to safeguard progressive values in California. The Legislature earlier this year also authorized giving $50 million to California’s Department of Justice and other legal groups, which has resulted in more than 40 lawsuits against the administration.

Bellisle reported from Seattle. Tran Nguyen reported from Sacramento.