Preemption in the context of the Supremacy Clause refers to the legal doctrine that when federal law conflicts with state law, the federal law takes precedence and displaces the state law. This principle is grounded in the Supremacy Clause found in Article VI, Clause 2 of the U.S. Constitution, which declares that the Constitution, federal laws made pursuant to it, and treaties are the "supreme Law of the Land" and override conflicting state laws
. There are two main types of preemption under the Supremacy Clause:
- Express Preemption: This occurs when a federal statute explicitly states that it overrides state law on a particular subject. For example, some federal laws include clear language that preempts state laws, effectively nullifying them or barring states from legislating on that matter
- Implied Preemption: This happens when preemption is not explicitly stated but can be inferred from the structure and purpose of federal law. Implied preemption is further divided into:
- Conflict Preemption: When it is impossible to comply with both federal and state laws simultaneously, or when state law obstructs the objectives of federal law, the state law is preempted
* **Field Preemption:** When federal regulation is so comprehensive in a particular area that it is inferred Congress intended to occupy the entire regulatory field, leaving no room for state laws
The Supreme Court uses congressional intent as the primary guide to determine whether preemption applies, often applying a "presumption against preemption," meaning federal law should not be interpreted to override state law unless Congress's intent to do so is clear
. In summary, preemption under the Supremacy Clause ensures that valid federal laws take priority over conflicting state laws, maintaining a hierarchy in the U.S. legal system where federal authority is supreme in cases of conflict
