Preemption, when a higher level of government restricts or withdraws the authority of a lower level of government to act on a particular issue, was historically used as a point of negotiation in the legislative process.

What is the purpose of preemption?

Preemption occurs when, by legislative or regulatory action, a “higher” level of government (state or federal) eliminates or reduces the authority of a “lower” level over a given issue. Express preemption occurs when a law contains a preemption clause or other explicit preemptive language.

What's an example of preemption?

Preemption applies regardless of whether the conflicting laws come from legislatures, courts, administrative agencies, or constitutions. For example, the Voting Rights Act, an act of Congress, preempts state constitutions, and FDA regulations may preempt state court judgments in cases involving prescription drugs.