This book examines the theory, law, and reality of preemption choice. The Constitution s federalist structures protect states sovereignty but also create a powerful federal government that can preempt and thereby displace the authority of state and local governments and courts to respond to a social challenge. Despite this preemptive power, Congress and agencies have seldom preempted state power. Instead, they typically have embraced concurrent, overlapping power. Recent legislative, agency, and court actions, however, reveal a newly aggressive use of federal preemption, sometimes even...