Constitutional Law I
Congress can preempt valid state laws by passing valid federal laws first pursuant to the Supremacy Clause.
Preemption may be either express or implied.
Express preemption requires explicit preemptive language in a federal law that defines the existence and scope of the preemption.
Preemption can also be implied. This can take the form of either field preemption or conflict preemption.
Field Preemption occurs when federal law leaves no doubt that Congress intended to occupy an entire field.
This can be detected in several ways:
- The federal regulation being so pervasive to imply that Congress intended to displace state regulatory authority
- The federal law touches a field in which the federal interest is so dominant that the federal system is assumed to preclude enforcement of state laws on the subject
- The object sought to be obtained by the federal law and the character of obligations imposed by it reveal a congressional intent to fully occupy the field
Conflict preemption can occur in two ways, impossibility and standing as an obstacle.
Impossibility Conflict Preemption
Impossibility conflict preemption occurs when compliance with both state and federal law is literally impossible.
Obstacle Conflict Preemption
Obstacle conflict preemption is when a state law "stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress."