In Arizona v. United States, the Supreme Court unanimously agreed that the federal government has no basis to nullify the "show me your papers" provision of Arizona's immigration law. Conservatives Antonin Scalia and Clarence Thomas, moderate Anthony Kennedy, liberals Stephen Breyer and Ruth Bader Ginsburg -- even Obama appointee Sonia Sotomayor -- all shot down the administration's effort to stop that part of the law. (Obama appointee Elena Kagan stayed out of it because she had taken part in the action as a member of the administration.) Yet even with that unanimity -- a position supported, if the polls are...