Commenting on Geier v. American Honda Motor Co.
Preemption is probably the most frequently used constitutional doctrine in practice. It is the doctrine by which Congress supersedes state law and establishes uniform federal regulatory schemes to ensure the smooth functioning of the national economy. The Supreme Court, in an effort to cabin this immense congressional power, has traditionally applied a "presumption against preemption" - a rule of statutory interpretation under which federal law does not preempt state police powers absent clear congressional intent. The presumption has recently fallen into some disfavor, however, and the Court has ignored it in some prominent preemption cases.3 It remains viable, but its vitality is now in question.