In the complaint filed in March, the Justice Department asked a U.S. District Court to invalidate several state laws, including parts of the 2017 California Values Act, which stops state and local police from providing certain assistance to federal immigration authorities. [...]

As the late Justice Antonin Scalia explained in Printz v. United States (1997), "the Federal Government may neither issue directives requiring the States to address particular problems, nor command the States' officers, or those of their political subdivisions, to administer or enforce a federal regulatory program."

At issue in Printz were parts of the 1993 Brady Handgun Violence Prevention Act that required local police to help implement a federal gun control scheme. The Clinton administration argued that obstructionist local officials should not be allowed to thwart duly enacted national legislation, but the Court disagreed. The provisions were struck down as an unconstitutional "federal commandeering of state governments."

Sessions' case against portions of the California Values Act involves the same constitutional failing that Scalia identified in Printz. The feds may commandeer local police into administering neither federal gun control nor federal immigration policy.