The Supremacy Clause and Federal Preemption
The issue: How should courts determine whether a federal law preempts state law?

Article VI of the Constitution makes federal law "the supreme law of the land," notwithstanding the contrary law any state might have.  In the important 1958 case of Cooper v Aaron, in which the Court considered the efforts of state authorities to block integration of Little Rock's Central High School, the Court unanimously declared, "No state legislator or executive or judicial official can war against the Constitution without violating his undertaking to support it....If the legislatures of the several states may at will, annul the judgments of the courts of the United States and destroy the rights acquired under those judgments, the Constitution itself becomes a mockery."  Federal law, not state law, is "the supreme law of the land." Despite the efforts of some states, even today, to "nullify" federal laws they disapprove of, few things in constitutional law are any clearer than the fact that any such efforts are grossly unconstitutional.  What remains a much more difficult question under Article VI is when a state law or action, which is at least arguably consistent with federal law, in fact creates sufficient conflict so as to justify finding it "preempted."


The preemption doctrine derives from the Supremacy Clause of the Constitution which states that the "Constitution and the laws of the United States...shall be the supreme law of the land...anything in the constitutions or laws of any State to the contrary notwithstanding."  This means of course, that any federal law--even a regulation of a federal agency--trumps any conflicting state law.

Preemption can be either express or implied.  When Congress chooses to expressly preempt state law, the only question for courts becomes determining whether the challenged state law is one that the federal law is intended to preempt.  Implied preemption presents more difficult issues, at least when the state law in question does not directly conflict with federal law.  The Court then looks beyond the express language of federal statutes to determine whether Congress has "occupied the field" in which the state is attempting to regulate, or whether a state law directly conflicts with federal law, or whether enforcement of the state law might frustrate federal purposes.

Federal "occupation of the field" occurs, according to the Court in Pennsylvania v Nelson (1956), when there is "no room" left for state regulation.  Courts are to look to the pervasiveness of the federal scheme of regulation, the federal interest at stake, and the danger of frustration of federal goals in making the determination as to whether a challenged state law can stand.

Pennsylvania vs Nelson 350 U.S. 497 (1956)

Pennsylvania v Nelson is an example of implied preemption challenge.  Here's language from Chief Justice Warren's opinion for the Court, striking down a Pennsylvania law making it a state crime to advocate the violent overthrow of the United States government:

"As was said by Mr. Justice Holmes in Charleston & Western Carolina R. Co. v. Varnville Furniture Co:"When Congress has taken the particular subject matter in hand, coincidence is as ineffective as opposition, and a state law is not to be declared a help because it attempts to go farther than Congress has seen fit to go."

Second, the federal statutes "touch a field in which the federal interest is so dominant that the federal system [must] be assumed to preclude enforcement of state laws on the same subject." Congress has devised an all-embracing program for resistance to the various forms of totalitarian aggression. Our external defenses have been strengthened, and a plan to protect against internal subversion has been made by it. It has appropriated vast sums, not only for our own protection, but also to strengthen freedom throughout the world. It has charged the Federal Bureau of Investigation and the Central Intelligence Agency with responsibility for intelligence concerning Communist seditious activities against our Government, and has denominated such activities as part of a world conspiracy. It accordingly proscribed sedition against all government in the nation -- national, state and local. Congress declared that these steps were taken "to provide for the common defense, to preserve the sovereignty of the United States as an independent nation, and to guarantee to each State a republican form of government. . . . "

Congress having thus treated seditious conduct as a matter of vital national concern, it is in no sense a local enforcement problem. As was said in the court below:  "Sedition against the United States is not a local offense. It is a crime against the Nation. As such, it should be prosecuted and punished in the Federal courts, where this defendant has, in fact, been prosecuted and convicted and is now under sentence.  It is not only important, but vital, that such prosecutions should be exclusively within the control of the Federal Government. . . . "

Third, enforcement of state sedition acts presents a serious danger of conflict with the administration of the federal program. Since 1939, in order to avoid a hampering of uniform enforcement of its program by sporadic local prosecutions, the Federal Government has urged local authorities not to intervene in such matters, but to turn over to the federal authorities immediately and unevaluated all information concerning subversive activities...."

In Silkwood v Kerr-McGee (1984), the Court, voting 5-4,  found that a $10 million dollar punitive damages award (in a case litigated by famed attorney Gerry Spence) against a nuclear power plant for negligently allowing employee (and union activist) Karen Silkwood to be contaminated with plutonium was not impliedly pre-empted by federal law.  Even though the Court had recently held that state regulation of the safety aspects of a federally-licensed nuclear power plant was preempted, the Court drew a different conclusion with respect to Congress's desire to displace state tort law--even though the tort actions might be premised on a violation of federal safety regulations.

Cipollone v Liggett Group (1992) was a closely-watched case concerning the extent of an express preemption provision in two cigarette labeling laws of the 1960s.  The case was a wrongful death action brought against tobacco companies on behalf of Rose Cipollone, a lung cancer victim who had started smoking cigarette in the 1940s.  The Court considered the preemptive effect on state law of a provision that stated "No requirement based on smoking and health shall be imposed under state law with respect to the advertising and promotion of cigarettes."  The Court concluded that several types of state tort actions were preempted by the provision, but allowed other types to go forward.  Perhaps the most interesting aspect of the case, from a constitutional standpoint, is the debate between justices over whether express preemption provisions should be read narrowly (a view adopted by seven justices) or read normally (a view favored by Justices Thomas and Scalia).

In American Insurance Association v Garamendi (2003), the Court considered the constitutionality of a California law designed to help California Holocaust survivors collect on unpaid insurance claims from German insurance companies.  Despite the absence of any clear statement in any executive agreement preempting state laws such as that of California, the Court, voting 5 to 4, found that the state Act conflicted with national policy and "stands in the way of [the President’s] diplomatic objectives.” The four dissenters included both liberals (Ginsburg and Stevens) and conservatives (Scalia and Thomas).  The dissenters argued, "Courts step out of their proper role when they rely on no legislative or even executive text, but only on inference and implication, to preempt state laws on foreign affairs grounds."

Gonzales v Oregon (2006) considered whether Congress, in enacting the Controlled Substances Act, intended to pre-empt state laws such as that of Oregon's which authorized physicians (under strictly controlled circumstances) to prescribe lethal doses of controlled drugs for terminally ill patients.  (The case also raised the administrative law issue of whether the Attorney General acted within the scope of his statutory authority when he issued regulations criminalizing the prescription of lethal drugs by physicians.)  The Court, ruling 5 to 4, held that the Act did not authorize pre-emption of Oregon's Death with Dignity Act.

In Arizona v Inter Tribal Council of Arizona (2013), the Court considered whether an Arizona law requiring voters in federal elections to provide actual proof of citizenship was trumped by a federal regulation that provided that it was sufficient for voters to simply assert under oath that they were citizens of the United States.  Voting 7 to 2, the Court concluded that the National Voter Registration Act, requiring states to "accept and use" the uniform federal voter law preempted Arizona's law requiring additional proof of citizenship in the form of documents such as passports or birth certificates.  Shortly after the decision, Kansas Secretary of State Kris Kobach, who defended the Arizona law in court, announced that Kansas (which adopted a proof of citizenship requirement similar to Arizona's) would follow Arizona in adopting a two-tier election registration system, requiring proof of citizenship for voting in state elections but not in federal elections.  The ACLU promptly sued both Arizona and Kansas, alleging that different treatment of voters in elections violates the Constitution.

Kris Kobach


Supremacy Clause
Cooper v Aaron (1958)


Silkwood v Kerr-McGee Corp. (1984)
Cipollone v Liggett Group (1992)
American Insurance Ass'n v Garamendi (2003)
Gonzales v Oregon (2006)
Arizona v Inter Tribal Council of Arizona (2013)

Article. VI.

This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding. 

Nuclear worker and labor activist Karen Silkwood.  The Court found Silkwood's $10 million award against Kerr-McGee not to be preempted by federal law.  Mystery still surrounds her death.  To read more about the Silkwood case:  Silkwood Links.

Book on the Silkwood story.


1. Why would the framers insist that even the most insignificant federal regulations should trump even the most important of state constitutional provisions?
2.  If a state makes criminal an action using language identical to language in a federal statute criminalizing the same action, is the state law preempted?  Clearly, there would be no conflict between federal and state law, but might state criminal enforcement jeopardize federal enforcement, or might the federal government be seen as having occupied the field of criminal enforcement?  (See Pennsylvania v Nelson (1956), in which the Supreme Court found preempted a state sedition law virtually identical in its reach with the federal sedition law.)
3.  If the federal government has occupied a field of regulation, for preemption purposes it becomes important to precisely identify the boundaries of that field.  What suggestions to you have for how that inquiry ought to be conducted?
4.  Don't punitive damages against a nuclear plant have the same practical effect as direct state regulation of the plant?  What is the basis for finding the latter preempted but the former not in Silkwood?
5.  How should we read federal statutes for preemption purposes?  Should we read them normally, as Justices Thomas and Scalia contend, or should we read them narrowly ( a presumption against preemption) as the other justices in Cippollone argued?

1950 tobacco ad starring Ronald Reagan.


Frontline Site on Silkwood Story

Supreme Court Rules FDA Label Rules Do Not Impliedly Preempt State Tort Suits

March 4, 2009
"We start with the assumption that the historic police powers of the States were not to be superseded by the Federal Act unless that was the clear and manifest purpose of Congress."  (Justice Stevens in Levine v Wyeth (2009))

The Supreme Court ruled, 6 to 3, in Levine v Wyeth that state juries may award damages for harm from unsafe drugs even though their manufacturers had satisfied federal regulators.

The ruling, which could have significant implications beyond drug manufacturing, upheld a jury verdict of $6.7 million in favor of a musician from Vermont whose arm had to be amputated after she was injected with an antinausea drug. Diana Levine was given a shot of Wyeth's drug Phenergan, which caused irreversible gangrene.  The drug’s manufacturer, Wyeth, had argued that its compliance with the Food and Drug Administration’s labeling requirements should immunize it from lawsuits.

The Supreme Court recently ruled, in Riegel v. Medtronic (2008), that many state suits concerning injuries caused by medical devices were barred by the express language in a federal law.  Levine addressed implied pre-emption. 

Justice John Paul Stevens, writing for the majority, said Congress could have required pre-emption, but had not. “Evidently,” he said, “it determined that widely available state rights of action provided appropriate relief for injured consumers.”  Stevens wrote, "the “complex and extensive” regulatory history and background relevant to this case undercut the FDA’s recent pronouncements of pre-emption, as they reveal the longstanding coexistence of state and federal law and the FDA’s traditional recognition of state-law remedies....In short, Wyeth has not persuaded us that failure-to-warn claims like Levine’s obstruct the federal regulation of drug labeling. Congress has repeatedly declined to pre-empt state law, and the FDA’s recently adopted position that state tort suits interfere with its statutory mandate is entitled to no weight. Although we recognize that some state-law claims might well frustrate the achievement of congressional objectives, this is not such a case."

Justice Samuel A. Alito Jr., writing for the dissenters, said the court had turned "yesterday’s dissent into today’s majority opinion” and turned ordinary injury suits into a “frontal assault on the F.D.A.’s regulatory regime for drug labeling.”  Alito said, “This case illustrates that tragic facts make bad law.”

Bert Rein, a lawyer for Wyeth, said "Wyeth fully complied with federal law in its labeling of Phenergan,” and that the F.D.A. is “in the best position to weigh the risks and benefits of a medicine.”

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