SACRAMENTO — A far-reaching measure aimed at preventing California’s law enforcement officers from helping to carry out President Donald Trump’s promised crackdown on illegal immigration — best known as the “sanctuary state” bill — was signed into law Thursday, along with 10 other bills designed to protect undocumented immigrants.

California Democrats this year have led a sustained effort to thwart Trump’s immigration agenda, an initiative that began more than a month before the president’s inauguration. Senate Bill 54 and other laws taking effect in January are widely seen — by champions and foes — as the most extensive statewide protections anywhere in the nation for those fearing deportation.

“These are uncertain times for undocumented Californians and their families,” Gov. Jerry Brown wrote in his signing statement for SB 54 Thursday, “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.”

SB 54 was the centerpiece of California’s anti-Trump resistance on immigration issues. Introduced on the first day of the legislative session last December and passed in the session’s final hours, it was pushed by immigration and civil rights groups but fiercely fought by the powerful statewide sheriff’s association.

The bill’s signing came as a big relief to Yadira Sanchez, 26, an undocumented immigrant from Mexico who lives in Oakland and works with the California Immigrant Youth Justice Alliance. Brown’s decision, she said, reaffirms California’s position as a leader in defending immigrant rights.

“We’ve always been one of the few states that sends this message to the rest of the country that it is possible to win local victories and that those victories are very important, regardless of what is going on at a national level or in the federal government,” she said.

The bill will limit communication between California police officers and federal immigration agents about people detained by police or in jail awaiting trial. Exceptions include those who have been convicted of at least one of hundreds of serious crimes within the past 15 years and suspects in serious crimes punishable with prison time for which a judge has found probable cause. It also prohibits California officers from inquiring about a person’s immigration status.

“Signing of #SB54 comes at a critical time in US history,” Senate President Pro Tem Kevin de León, the bill’s author, tweeted Thursday. “With Donald Trump, we have witnessed a racial divide we have not seen in decades.”

Civil rights and immigration advocacy groups cheered SB 54’s passage. The move also had a symbolic resonance: Brown signed the landmark measure on the last day for young undocumented immigrants known as “Dreamers” to renew their protected status and work permits through a popular program known as DACA (Deferred Action for Childhood Arrivals). Trump announced last month he would be phasing out the program, but he said he would give Congress six months to pass similar protections into law for those brought into the country illegally as children.

“With this bill, the number of shameful deportation tactics will be stopped and prohibited, and others will be limited,” said Jon Rodney, a spokesman for the Oakland-based California Immigrant Policy Center. “It’s very important in terms of making sure that we don’t use our resources to help Trump deport millions of people and in recognizing that immigrants are such a vital part of California’s heart and soul.”

Brown’s signing of SB 54 was not a surprise. The governor negotiated last-minute changes to the bill with de León, a Los Angeles Democrat, including a significant expansion of exceptions to the new rules. The final version of the bill allows federal agents to conduct interviews with jail inmates, but it bars them from occupying permanent office space there. The changes also excluded state prisons from most of the law’s provisions.

The amendments, made to win Brown’s support, neutralized the opposition of the statewide police chiefs association. But many sheriffs — who oversee the state’s jails — remained opposed.

“Although we appreciate the governor’s efforts to mitigate the most dangerous provisions of SB 54, we are discouraged that this problematic bill has been signed into law,” California State Sheriffs’ Association President Bill Brown said in a statement.  “We will continue to work to address the bill’s liabilities, which include restricting our communications with federal law enforcement about the release of wanted, undocumented criminals from our jails, including repeat drunk drivers, persons who assault peace officers, serial thieves, animal abusers, known gang members and other serious offenders.”

Those on both sides of the issue took to social media Thursday to celebrate or bemoan the passage of SB 54. Proponents said it will make communities safer by encouraging undocumented crime victims to come forward, while opponents framed it as an overreach that will protect criminals at the expense of law-abiding citizens and further heighten tensions between California and the federal government.

U.S. Attorney General Jeff Sessions has already threatened to sanction “sanctuary cities” by withholding law enforcement grants, an announcement that prompted lawsuits from California and other state. Some opponents of the bill believe it violates federal law by limiting cooperation between federal and local law enforcement agents.

“It’s significant in the fact that it now gives Jeff Sessions what he needs if he wants to pursue a lawsuit against California,” said Ira Mehlman, a spokesman for the Washington, D.C.-based Federation for American Immigration Reform, which advocates for immigration controls and stricter enforcement.

“I think they’re trying to test just how far they can push the federal government,” Mehlman said of California lawmakers, “and we certainly expect the federal government will respond.”

Perhaps anticipating his critics, Brown in his signing message tried to clarify what SB 54 would — and wouldn’t — do.

“This bill does not prevent or prohibit Immigration and Customs Enforcement or the Department of Homeland Security from doing their own work in any way,” he wrote. “They are free to use their own considerable resources to enforce federal immigration law in California.”

Other bills Brown signed Thursday include measures to protect undocumented immigrants from housing discrimination, workplace raids and block the expansion of immigration detention centers.

Senate Bill 29, by Sen. Ricardo Lara, D-Bell Gardens, places a moratorium on new or renewed leases between local governments and for-profit immigration detention centers.

Thursday’s signings mark “quite a change” since the passage of Proposition 187, a 1994 ballot initiative that prohibited undocumented immigrants from obtaining public benefits — including schooling — in the Golden State, said Samuel Molina, California director of the national immigrant advocacy organization Mi Familia Vota, or “My Family Votes.” Most of the measure was eventually struck down in federal courts.

Sampling of immigration bills signed into law

‘Sanctuary state’: Senate Bill 54, by Senate Leader Kevin de León, D-Los Angeles, aims to prevent local law enforcement officers from assisting with President Trump’s promised crackdown on illegal immigration by restricting communication and coordination between local officers and federal agents about people in custody, with the exception of those convicted of most felonies within the past 15 years.

Landlords and housing: Assembly Bill 291, by Assemblyman David Chiu, D-San Francisco, will make it illegal for landlords to use someone’s real or perceived immigration status against them. Assembly Bill 299, by Assemblyman Ian Calderon, D-Whittier, would bar public entities from seeking information from property managers about a tenant’s immigration status.

Workplace raids: Another bill by Chiu, Assembly Bill 450, was carried in anticipation of stepped-up workplace immigration raids. It will call on an employer to require proper court documents before allowing immigration agents access to the workplace or to employee information.

‘Dreamer’ and student protections: Assembly Bill 699 by Assemblyman Patrick O’Donnell, D-Long Beach, prevents schools from collecting information about the immigration status of students or their families and requires school officials to report requests for information or access to a school from immigration authorities to the governing board, among other measures. As soon as Trump announced he would be phasing out the Deferred Action for Childhood Arrivals (DACA) program, which grants work permits to young people brought into the country illegally as children (many of whom refer to themselves as “Dreamers”), California lawmakers introduced a number of bills, including Assembly Bill 21, by Assemblyman Ash Kalra, D-San Jose. It will require CSU and community colleges to expand protections for college DACA students and their families.

Immigration detention centers: Senate Bill 29, by Lara, places a moratorium on new or renewed contracts between local governments and corporations that run immigration detention centers.