Is California the next Little Rock? Recent statements by Attorney General Jeff Sessions suggest that it might be.

Last week I wrote about folks in California who want to split the state in various ways. But no sooner was that published than Sessions put California on notice in a blistering speech that invoked the American Civil War.

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“I understand that we have a wide variety of political opinions out there on immigration.  But the law is in the books and its purpose is clear,” Sessions told the California Peace Officers’ Association on Wednesday. “There is no nullification. There is no secession.  Federal law is ‘the supreme law of the land.’ I would invite any doubters to Gettysburg, and to the graves of John C. Calhoun and Abraham Lincoln.”

Sessions’ stern warning was prompted by California laws designed to frustrate the enforcement of federal immigration laws, as inspired by the “Sanctuary City” movement.

The attorney general has filed a lawsuit challenging three California laws: one prohibiting certain information-sharing between state and federal authorities, one that requires the California state attorney general to “inspect” any facilities holding illegal immigrants, and one that bars private employers from cooperating with federal authorities. According to the Justice Department, “The Supremacy Clause does not allow California to obstruct the United States’ ability to enforce laws that Congress has enacted or to take actions entrusted to it by the Constitution.”

Legally, this is a complicated matter. The federal government can’t force state officials to administer or execute a federal law. That’s called “commandeering” and it’s outside federal power according to both the Tenth Amendment and the Supreme Court case of Printz v. United States, which struck down a federal law that tried to force local law enforcement to perform background checks on gun purchases.

The feds can provide financial incentives for state and local officials to cooperate, but they can’t make them do anything if they don’t want to. If the feds want to enforce federal law and state and local officials don’t want to help, the feds must do it themselves, and pay the financial and political costs that go with it. On the other hand, states can’t interfere with the enforcement of federal law, either.

To the extent that California is actively interfering with federal immigration enforcement, as opposed to merely passively refusing to cooperate, the federal government may well have a case here. But I wonder if Sessions’ rather strong rhetoric points to a potential federal response that goes beyond litigation. It wouldn’t be the first time a president has sent troops to enforce federal law when local officials stood in the way.

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One famous example was President Eisenhower’s use of federal troops from the 101st Airborne to enforce the desegregation of Little Rock schools over the active opposition of Arkansas Gov. Orval Faubus. Faubus called out the Arkansas National Guard; Eisenhower issued an order placing the Guard under federal control, and then sent in approximately 1,000 federal troops.

Eisenhower’s authority for this was the Insurrection Act, a federal statute that authorizes the president to use federal forces to execute the law. Normally, this is done at the request of a state’s governor. However, if the governor fails to make such a request, the president can still invoke the Insurrection Act.

Louisiana Gov. Kathleen Blanco’s hesitance to make that request led to delays in the run-up to Hurricane Katrina in 2005. President George W. Bush’s reluctance to override Blanco, a female governor of a different party who had not consented to turning over authority to the federal government, was another cause of the delays. But President Trump is unlikely to be so circumspect.

The key section of the Insurrection Act provides: “Whenever the President considers that unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States, make it impracticable to enforce the laws of the United States in any state by the ordinary course of judicial proceedings,” the president may call the state’s National Guard into federal service, and employ whatever federal armed forces he considers necessary.

So at what point does California’s response move from passive resistance (which is permitted) to “unlawful obstructions, combinations … or rebellion against the authority of the United States?” I’m not sure, and I don’t think we’re there yet. But Sessions’ strong language suggests that he thinks we’re closer than we should be. Stay tuned.

Glenn Harlan Reynolds, a University of Tennessee law professor and the author of The New School: How the Information Age Will Save American Education from Itself, is a member of USA TODAY’s Board of Contributors. Follow him on Twitter: @instapundit.