Relation of Nation & States · NextGen UBE Constitutional Law
The Supremacy Clause
Article VI makes federal law "the supreme Law of the Land." When federal and state law conflict, federal law prevails. Preemption is the doctrine that determines when state law must yield to federal law.
Three types of preemption
Express preemption: Congress explicitly says state law is preempted. Field preemption: Federal regulation is so pervasive it occupies the entire field. Conflict preemption: State law conflicts with federal law through impossibility or obstacle preemption. A presumption against preemption applies in areas of traditional state regulation.
Presumption against preemption
In areas of traditional state regulation (health, safety, land use), courts presume Congress did not intend to preempt unless there is clear evidence. This presumption does not apply in areas traditionally occupied by the federal government (immigration, foreign affairs).
Express preemption
Congress includes explicit preemption language in the statute. The scope depends on statutory interpretation of the preemption clause. Key question: How broadly does the express preemption clause sweep? (E.g., does it preempt all state regulation, or only specific types?)
Field preemption
Even without express preemption language, state law is preempted if the federal regulatory scheme is so pervasive that Congress left no room for supplementary state regulation, or the federal interest is so dominant that federal law precludes enforcement of state laws on the same subject.
Conflict preemption — impossibility
State law is preempted if it is physically impossible to comply with both state and federal law simultaneously. Courts apply this narrowly: mere difficulty is not impossibility.
Conflict preemption — obstacle
State law is preempted if it "stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress." This is the broadest and most contested form — it requires determining congressional purpose and assessing whether state law frustrates it.