The claim: 

In one of his opening broadsides against the Golden State just weeks after his inauguration, Trump denounced California as “out of control” for its “sanctuary state” policy on immigration. And again, as he occasionally does when he and California are at odds, he threatened to pull the state’s federal funding. The threat was soon followed by an executive order to cut specified federal crime-fighting grants to the state. Then came the lawsuit: In March 2018, the U.S. Justice Department sued California to invalidate three state laws that make it harder for federal immigration agents to arrest and detain suspected undocumented immigrants. 

California’s sanctuary policies are illegal and unconstitutional and put the safety and security of our entire nation at risk. Thousands of dangerous & violent criminal aliens are released as a result of sanctuary policies, set free to prey on innocent Americans. THIS MUST STOP!

— Donald J. Trump (@realDonaldTrump) March 13, 2018

The facts:

What is California’s “sanctuary state” policy? The three California laws at issue: 

• Restrict state and local police from cooperating with federal immigration agents
• Require employers to alert their employees before any federal immigration inspections and prohibit them from allowing such inspections if federal agents do not present a warrant
• Subject immigration detention facilities to additional state oversight

None of those state laws mandate the release of undocumented immigrants, so the claim by the president that “thousands of dangerous (and) violent criminal aliens” have been released as a result of California’s sanctuary policies is wrong. So far, courts have not allowed the Trump administration to make federal funding conditional on repealing these laws.

But whether the three laws are illegal or unconstitutional is an unsettled question. California and other like-minded cities and states have long argued that the U.S. government cannot compel state and local law enforcement agencies to enforce federal law. If that line of argument rings a bell, it’s the same “states’ rights” argument, grounded in the 10th Amendment of the U.S. Constitution, that the political right has used for generations. 

Lower courts have already struck down parts of the California law that govern employers. But in a decisive win for California in June 2020, the U.S. Supreme Court declined to hear the Department of Justice’s challenge to the state law that prevents state and local cops from cooperating with immigration authorities.