Today, Texas Governor Greg Abbott signed into law S.B. 4. This law makes it a state offense to illegally cross the border. Before you shout that this law clearly violates Arizona v. United States (2012), re-read this passage from Justice Kennedy's majority opinion:
However the law is interpreted, if §2(B) only requires state officers to conduct a status check during the course of an authorized, lawful detention or after a detainee has been released, the provision likely would survive pre-emption—at least absent some showing that it has other consequences that are adverse to federal law and its objectives. There is no need in this case to address whether reasonable suspicion of illegal entry or another immigration crime would be a legitimate basis for prolonging a detention, or whether this too would be preempted by federal law. See, e.g., United States v. Di Re, 332 U.S. 581, 589 (1948) (authority of state officers to make arrests for federal crimes is, absent federal statutory instruction, a matter of state law); Gonzales v. Peoria, 722 F.2d 468, 475–476 (CA9 1983) (concluding that Arizona officers have authority to enforce the criminal provisions of federal immigration law), overruled on other grounds in Hodgers-Durgin v. de la Vina, 199 F.3d 1037 (CA9 1999).
Arizona left open the question of whether Texas can detain aliens who violated federal immigration law. I made this point in the New York Times in October:
