Administration officials allege the laws, passed by the Legislature last year and signed by Brown, blatantly obstruct federal immigration law and thus violate the Constitution's supremacy clause, which gives federal law precedence over state enactments.
State Attorney General Xavier Becerra has pledged to defend the measures in court, saying they work in concert with federal laws. "Our teams work together to go after drug dealers, to combat gang violence, to take down sex-trafficking rings, and we have no intention of changing that," he said Wednesday.
In his speech to more than 100 police chiefs, sheriffs and other law enforcement officers, Sessions argued that the Trump administration did not reject immigration, but said the U.S. should not reward those who unlawfully enter the country with benefits, such as legal status, food stamps and work permits.
He argued the federal government sued California to invalidate and immediately freeze what he called unjust laws.
"We are going to fight these irrational, unfair and unconstitutional policies that have been imposed on you and our federal officers," Sessions said as he finished his speech, and some officers stood in ovation. "You can be certain about this: We have your back, and you have our thanks."
As the group welcomed Sessions with applause, a statewide coalition of immigrant rights groups gathered outside to protest his arrival.
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The event is usually a time for law enforcement officers to mingle with lawmakers, lobby for legislation and receive guidance from leaders on law enforcement priorities across the state. But Sessions' appearance swept the attention away.
Police officers said the state's immigration laws had not impeded their jobs so far, but the constant battles between state and federal leaders were affecting their relationships with federal partners. Fairfield Police Chief Randy Fenn said the lawsuit raised concerns about whether law enforcement agencies would be caught in the middle of a larger immigration battle.
"We are waiting to see how this shakes out," Fenn said.
Neil Gallucci, second vice president of the state peace officers group, said Sessions' opinion was important to understand as the federal lawsuit had the potential to change California laws.