# Arizona v. United States **Status: stub — expand.** **Decided June 25, 2012 · 5–3 · Kennedy, J.** The leading modern immigration-preemption case, striking three of four challenged provisions of Arizona's SB 1070. Preempted: making failure to carry federal registration papers a state crime (**field** preemption — the federal registration scheme is complete); making it a state crime for an unauthorized immigrant to seek work (**conflict** preemption — Congress deliberately declined to penalize the employee); and authorizing warrantless arrest on probable cause of a removable offense (conflict — it gave state officers discretion federal officers lack). Upheld, at least facially: § 2(B), the "show me your papers" provision requiring officers to check immigration status during lawful stops, since a status **inquiry** does not conflict with federal law. The Court left it open to as-applied challenge. The framing holding is broader than the provisions: "The Government of the United States has broad, undoubted power over the subject of immigration," derived from enumerated powers and the sovereign attributes of foreign relations. It is the field-preemption anchor for every state-immigration conflict since. ## See also - [[Federal Preemption]] · [[Sanctuary Jurisdiction]] · [[Federalism Powers Crosswalk]]