The Supreme Court handed down a major immigration ruling today in the case of Chamber of Commerce v. Whiting. At issue was the Legal Arizona Workers Act, a controversial state law that requires all Arizona employers to confirm the legal status of their workers via E-Verify, the federal electronic verification system. Under the law, the state may impose draconian penalties, including the loss of business licenses, on those firms that hire unauthorized aliens. The Chamber of Commerce, which brought the suit, calls the law a “business death penalty” and, in a notable twist, the Chamber’s allies in the fight included leading liberal groups such as the Service Employees International Union, the Southern Poverty Law Center, the National Immigrant Justice Center, and the National Council of La Raza.

The question before the Supreme Court was whether the Arizona statute conflicts with federal immigration law and is therefore preempted by the “comprehensive scheme” Congress developed to address the matter. In a divided ruling that split along conservative-liberal lines (with Justice Elena Kagan recused), Chief Justice John Roberts dismissed the Chamber’s arguments and ruled that Arizona’s actions are perfectly permissible. Not only will this decision clear the way for similar laws in other states, it serves as a potential preview for the legal battle over Arizona’s notorious Support Our Law Enforcement and Safe Neighborhoods Act, which requires police officers to “make a reasonable attempt” to determine the immigration status of anyone they encounter through “any lawful stop, detention, or arrest.” As my colleague Jacob Sullum has observed, under that law “even legal permanent residents and U.S. citizens—who are under no obligation to carry Arizona-approved identification but could be detained if they don't—would be subject to ‘distinct, unusual and extraordinary burdens’ because of the way they look and sound.”

The Obama admnistration's legal argument against this "papers please" law also raises the question of federal preemption, and today’s decision in Whiting doesn’t bode well for the challenge.