Federal preemption

In the law of the United States, federal preemption is the invalidation of a U.S. state law that conflicts with federal law. According to the Supremacy Clause (Article VI, clause 2) of the United States Constitution, As the Supreme Court stated in Altria Group v. Good, 555 U.S. 70 (2008), a federal law that conflicts with a state law will trump, or 'preempt', that state law: Although many concurrent powers are subject to federal preemption, some are usually not, such as the power to tax private citizens. In Altria Group v. Good, the Court wrote: In Wyeth v. Levine (2009), the Court emphasized what it called the 'two cornerstones' of pre-emption jurisprudence: See also Reilly, 533 U. S., at 541–542 (citation omitted):