Duhaime's Law Dictionary

Preemption Doctrine Definition:

The superceding of any lower jurisdiction's law in the event of a law on topic extant within a higher jurisdiction.

US flag In Musewicz v Cordara, Justice Flaherty of the Commonwealth Court of Pennsylvania used these words:

"[P]reempts may be understood as a synonym for supersedes. Preemption ... applies to situations where a higher authority (in this case, the State) regulates an area so comprehensively and pervasively as to preclude the coexistence of regulation by a lower authority (in this case, the County)."

Madam Justice Nancy Saitta of the Supreme Court of Nevada offered a complete description in Nanopierce Technologies:

"The preemption doctrine, which provides that federal law supersedes conflicting state law, arises from the Supremacy Clause of the United States Constitution. The Supremacy Clause, found in Article VI, requires that "the laws of the United States . . . shall be the supreme law of the land ... any thing in the Constitution or laws of any State to the contrary notwithstanding.

"Thus, when a conflict exists between federal and state law, valid federal law overrides, i.e., preempts, an otherwise valid state law. Whether a federal enactment preempts state law is fundamentally a question of congressional intent—did Congress expressly or impliedly intend to preempt state law? Even when implied, Congress's intent to preempt state law, in light of a strong presumption that areas historically regulated by the states generally are not superseded by a subsequent federal law, must be clear and manifest.

"Express preemption: Congress expressly preempts state law when it explicitly states that intent in a statute's language.Thus, when determining whether Congress has expressly preempted state law, a court must examine statutory language—any explicit preemption language generally governs the extent of preemption.

"Implied preemption: When Congress does not include statutory language expressly preempting state law, Congress's intent to preempt state law nonetheless may be implied in two circumstances known as field preemption and conflict preemption.

"First, under field preemption, preemption is implied when congressional enactments so thoroughly occupy a legislative field, or touch a field in which the federal interest is so dominant, that Congress effectively leaves no room for states to regulate conduct in that field. To determine whether Congress has preempted a field of law, the entire regulatory scheme must be examined to determine whether, based on its level of comprehensiveness or the nature of the field regulated, Congress intended to preclude states from also imposing requirements on that field. If, based on that examination, it can be inferred that Congress intended to occupy that legislative field, state requirements are preempted regardless of any specific law's conflict.

"Second, even when Congress's enactments do not pervade a legislative field or regulate an area of uniquely federal interest, Congress's intent to preempt state law is implied to the extent that federal law actually conflicts with any state law. Conflict preemption analysis examines the federal statute as a whole to determine whether a party's compliance with both federal and state requirements is impossible or whether, in light of the federal statute's purpose and intended effects, state law poses an obstacle to the accomplishment of Congress's objectives."


  • Musewicz v. Cordaro, 925 A. 2d 172 (2006)
  • Nanopierce Tech. v. Depository Trust, 168 P. 3d 73 (2006)

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