Obama v. Arizona

Weekly Standard  "In fact, the Obama administration goes so far as to assert that S.B. 1070 prevents it from getting tough on truly nasty illegal immigrants: "S.B. 1070 disrupts federal enforcement priorities and resources that focus on aliens who pose a threat to national security or public safety ... undermin[ing] the federal government's careful balance of immigration enforcement policies and objectives."
"But that line of argument wholly misses the point. When courts decide whether federal law preempts state law, the question is not whether the state law conflicts with the president's selective enforcement of federal statutes. The question is whether the state law "stands as an obstacle to the accomplishment ... of the full purposes and objectives of Congress," as embodied by the federal statutes. S.B. 1070 satisfies that test – it does nothing more than allow state officials to enforce Congress's purposes and objectives as expressed in current federal statutes." Emphasis added.