Federal Preemption: A Legal Primer

July 23, 2019 – May 18, 2023 R45825

Federal Preemption: A Legal Primer
May 18, 2023
The Constitution’s Supremacy Clause provides that federal law is “the supreme Law of
the Land” notwithstanding any state law to the contrary. This language is the foundation
Bryan L. Adkins
for the doctrine of federal preemption, according to which federal law supersedes
Legislative Attorney
conflicting state laws. The Supreme Court has identified two general ways in which

federal law can preempt state law. First, federal law can expressly preempt state law
Alexander H. Pepper
when a federal statute or regulation contains explicit preemptive language. Second,
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federal law can impliedly preempt state law when Congress’s preemptive intent is

implicit in the relevant federal law’s structure and purpose.
Jay B. Sykes
Legislative Attorney
In both express and implied preemption cases, the Supreme Court has made clear that

Congress’s purpose is the “ultimate touchstone” of its statutory analysis. In analyzing
congressional purpose, the Court has at times applied a canon of statutory construction

known as the “presumption against preemption,” which instructs that federal law should
not be read as superseding states’ historic police powers “unless that was the clear and manifest purpose of
Congress.”
In cases involving express preemption, the Supreme Court’s decisions have depended heavily on the details of
particular statutory schemes, but the Court has assigned some phrases specific meanings even when they have
appeared in different statutory contexts. The Court also must sometimes interpret savings clauses—statutory
provisions designed to insulate certain categories of state law from federal preemption.
In implied preemption cases, the Court has identified two subcategories of implied preemption: field preemption
and conflict preemption.
Field preemption occurs when a pervasive scheme of federal regulation implicitly precludes supplementary state
regulation or when states attempt to regulate a field where there is a sufficiently dominant federal interest.
Applying these principles, the Court has held that federal law occupies a number of regulatory fields, including
alien registration, nuclear safety regulation, and the regulation of locomotive equipment.
Conflict preemption, in contrast, occurs when simultaneous compliance with both federal and state regulations is
impossible (impossibility preemption) or when state law poses an obstacle to the accomplishment of federal goals
(obstacle preemption).
The Court’s cases recognizing impossibility preemption are not limited to instances in which compliance with
federal and state law is impossible in a literal sense. Rather, the Court has held that compliance with both federal
and state law can be “impossible” even when a regulated party can petition the federal government for permission
to comply with state law or avoid violations of the law by refraining from selling a regulated product altogether.
In its obstacle preemption decisions, the Court has concluded that state law can interfere with federal goals by
frustrating Congress’s intent to adopt a uniform system of federal regulation; conflicting with Congress’s goal of
establishing a regulatory ceiling for certain products or activities; or by impeding the vindication of a federal
right.

Congressional Research Service

Federal Preemption: A Legal Primer

he Constitution’s Supremacy Clause provides that “the Laws of the United States . . . shall
be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any
T Thing in the Constitution or Laws of any State to the Contrary notwithstanding.”1 This
language is the foundation for the doctrine of federal preemption, under which federal law
supersedes conflicting state laws.2
Federal preemption of state law is a ubiquitous feature of the modern regulatory state and “almost
certainly the most frequently used doctrine of constitutional law in practice.”3 Preemptive federal
statutes shape the regulatory environment for most major industries, including drugs and medical
devices, banking, air transportation, securities, automobile safety, and tobacco.4
As a result, disputes over preemption “rage in the courts, in Congress, before agencies, and in the
world of scholarship.”5 These debates implicate many of the themes that recur throughout both
the Supreme Court’s preemption case law and the federalism literature. Proponents of broad
federal preemption often cite the benefits of uniform national regulations6 and the concentration
of expertise in federal agencies.7 Opponents typically appeal to the importance of policy
experimentation,8 the greater democratic accountability that they believe accompanies state and

1 U.S. CONST. art. VI, cl. 2.
2 Murphy v. Nat’l Collegiate Athletic Ass’n, 138 S. Ct. 1461, 1479 (2018); Gade v. Nat’l Solid Wastes Mgmt. Ass’n,
505 U.S. 88, 108 (1992).
3 Stephen A. Gardbaum, The Nature of Preemption, 79 CORNELL L. REV. 767, 768 (1994). See also Jamelle C. Sharpe,
Toward (a) Faithful Agency in the Supreme Court’s Preemption Jurisprudence, 18 GEO. MASON L. REV. 367, 367
(2011) (“Preemption has become one of the most frequently recurring and perplexing public law issues facing the
federal courts today.”); Garrick B. Pursley, Preemption in Congress, 71 OHIO ST. L. J. 511, 514 (2010) (describing
preemption as “the issue of constitutional law that most directly impacts everyday life”); Thomas W. Merrill,
Preemption and Institutional Choice, 102 NW. U. L. REV. 727, 730 (2008) (noting that “[p]reemption is one of the most
widely applied doctrines in public law”).
4 Pursley, supra note 3, at 513.
5 William W. Buzbee, Introduction, in PREEMPTION CHOICE: THE THEORY, LAW, AND REALITY OF FEDERALISM’S CORE
QUESTION 1, 1 (William W. Buzbee ed., 2009).
6 See Alan Untereiner, The Defense of Preemption: A View From the Trenches, 84 TUL. L. REV. 1257, 1262 (2010)
(arguing that the “multiplicity of government actors below the federal level virtually ensures that, in the absence of
federal preemption, businesses with national operations that serve national markets will be subject to complicated,
overlapping, and sometimes even conflicting legal regimes”); Brief for the Chamber of Commerce of the United States
of America as Amicus Curiae at 20, Geier v. Am. Honda Motor Co., No. 98-1811 (U.S. Nov. 19, 1999), 1999 WL
1049891 (arguing that “common-law decisionmaking is notoriously ill-suited to the establishment of nationwide
standards that strike the proper balance among the multitude of societal interests at stake in a particular regulatory
setting”).
7 See Untereiner, supra note 6, at 1262 (“In many cases, Congress’s adoption of a preemptive scheme . . . ensures that
the legal rules governing complex areas of the economy or products are formulated by expert regulators with a broad
national perspective and needed scientific or technical expertise, rather than by decision makers—such as municipal
officials, elected state judges, and lay juries—who may have a far more parochial perspective and limited set of
information.”).
8 See Charles W. Tyler & Heather K. Gerken, The Myth of the Laboratories of Democracy, 122 COLUM. L. REV. 2187,
2230 (2022) (“[W]herever [preemption] exists, federal law displaces state law, thereby ‘stifling state-by-state diversity
and experimentation’ . . . .”); Ernest A. Young, Making Federalism Doctrine: Fidelity, Institutional Competence, and
Compensating Adjustments, 46 WM. & MARY L. REV. 1733, 1850 (2004) (“Preemption doctrine . . . goes to whether
state governments actually have the opportunity to provide beneficial regulation for their citizens; there can be no
experimentation or policy diversity, and little point to citizen participation, if such opportunities are supplanted by
federal policy.”).
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local regulation,9 and the gap-filling role of state common law in deterring harmful conduct and
compensating injured plaintiffs.10
In addition to these general normative disputes, preemption decisions also raise narrower
interpretive issues.
As Figure 1 illustrates, the Supreme Court has identified two general types of preemption. First,
federal law can expressly preempt state law when a federal statute or regulation contains explicit
preemptive language. Second, federal law can impliedly preempt state law when its structure and
purpose implicitly reflect Congress’s preemptive intent.11
The Court has identified two subcategories of implied preemption: field preemption and conflict
preemption.
Field preemption occurs when a pervasive scheme of federal regulation implicitly precludes
supplementary state regulation or when states attempt to regulate a field where the federal interest
is sufficiently dominant.12
In contrast, conflict preemption occurs when compliance with both federal and state regulations is
impossible (impossibility preemption)13 or when state law poses an “obstacle” to the
accomplishment of the “full purposes and objectives” of Congress (obstacle preemption).14

9 See Robert R.M. Verchick & Nina Mendelson, Preemption and Theories of Federalism, in PREEMPTION CHOICE: THE
THEORY, LAW, AND REALITY OF FEDERALISM’S CORE QUESTION 13, 17 (William W. Buzbee ed., 2009) (“Citizens are
often presumed to be able to participate more directly in policy making at the state level. Greater state autonomy to
regulate will mean more opportunities for citizens to participate in governance and seek responsive government.”);
Roderick M. Hills, Jr., Against Preemption: How Federalism Can Improve the National Legislative Process, 82 N.Y.U.
L. REV. 1, 4 (2007) (“Federalism’s value, if there is any, lies in the often competitive interaction between the levels of
government. In particular, a presumption against federal preemption of state law makes sense not because states are
necessarily good regulators of conduct within their borders, but rather because state regulation makes Congress a more
honest and democratically accountable regulator of conduct throughout the nation.”).
10 Thomas O. McGarity, THE PREEMPTION WAR: WHEN FEDERAL BUREAUCRACIES TRUMP LOCAL JURIES 237 (2008)
(“The common law provides an effective vehicle for filling the regulatory gaps that inevitably arise at the
implementation stage because agencies can never anticipate and regulate every potentially socially undesirable aspect
of an ongoing business and cannot possibly envision all of the possible ways that regulatees will react to regulatory
programs.”).
11 Gade v. Nat’l Solid Wastes Mgmt. Ass’n, 505 U.S. 88, 98 (1992).
12 Arizona v. United States, 567 U.S. 387, 399 (2012) (“[Congress’s] intent to displace state law altogether can be
inferred from a framework of regulation ‘so pervasive . . . that Congress left no room for the States to supplement it’ or
where there is a ‘federal interest . . . so dominant that the federal system will be assumed to preclude enforcement of
state laws on the same subject.’”) (quoting Rice v. Santa Fe Elevator Corp., 331 U.S. 218, 230 (1947)).
13 Fla. Lime & Avocado Growers, Inc. v. Paul, 373 U.S. 132, 142–43 (1963).
14 Hines v. Davidowitz, 312 U.S. 52, 67 (1941).
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Federal Preemption: A Legal Primer

Figure 1. Preemption Taxonomy

Source: CRS.
While the Supreme Court has repeatedly distinguished these preemption categories, it has also
explained that the presence of a preemption clause in a federal statute does not preclude the
possibility of implied preemption.15 Congress must therefore consider the possibility that courts
may construe statutes as impliedly preempting certain categories of state law even if such laws do
not fall within the explicit terms of a preemption clause.
This report provides a general overview of federal preemption to inform Congress as it crafts
laws implicating overlapping federal and state interests. The report begins by reviewing two
general principles that have shaped the Court’s preemption jurisprudence: the primacy of
congressional intent and the presumption against preemption.
The report then examines how courts have interpreted certain language that is commonly used in
preemption clauses. Next, the report reviews judicial interpretations of statutory savings
clauses—provisions that insulate certain categories of state law from federal preemption. Finally,
the report discusses the Court’s implied preemption case law by examining illustrative examples
of its field preemption, impossibility preemption, and obstacle preemption decisions.
General Preemption Principles
The Primacy of Congressional Intent
The Supreme Court has explained that in determining whether—and to what extent—federal law
preempts state law, the purpose of Congress is the “ultimate touchstone” of its statutory
analysis.16 The Court has further instructed that Congress’s intent is discerned “primarily” from a
statute’s text.17 The Court has also noted, however, the importance of statutory structure and
purpose in determining how Congress intended a federal regulatory scheme to interact with

15 Geier v. Am. Honda Motor Co., 529 U.S. 861, 881–82 (2000) (holding that a federal regulatory scheme impliedly
preempted state common law claims involving automobile safety, even though a preemption clause in the relevant
statute did not expressly encompass those claims).
16 Wyeth v. Levine, 555 U.S. 555, 565 (2009) (quoting Medtronic, Inc. v. Lohr, 518 U.S. 470, 485 (1996)).
17 Medtronic, 518 U.S. at 486.
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Federal Preemption: A Legal Primer

related state laws.18 Like many of its statutory interpretation cases, then, the Court’s preemption
decisions often involve disputes over the appropriateness of consulting extratextual evidence to
determine Congress’s intent.19
The Presumption Against Preemption
In evaluating congressional purpose, the Supreme Court has at times employed a canon of
construction called the “presumption against preemption,” which instructs that federal law should
not be read to preempt laws involving the states’ historic police powers20 “unless that was the
clear and manifest purpose of Congress.”21 The presumption is rooted in principles of federalism
and respect for state sovereignty.22 While the Court has described the presumption against
preemption as one of the “cornerstones” of its preemption jurisprudence, it has invoked the
presumption inconsistently.23

18 Id. (“Congress’ intent, of course, primarily is discerned from the language of the pre-emption statute and the
statutory framework surrounding it. Also relevant, however, is the structure and purpose of the statute as a whole, as
revealed not only in the text, but through the reviewing court’s reasoned understanding of the way in which Congress
intended the statute and its surrounding regulatory scheme to affect business, consumers, and the law.”) (citations and
internal quotation marks omitted).
19 See, e.g., Wyeth, 555 U.S. at 583 (Thomas, J., concurring in the judgment) (rejecting the Court’s obstacle preemption
jurisprudence as “inconsistent with the Constitution,” while noting that the Court “routinely invalidates state laws based
on perceived conflicts with broad federal policy objectives, legislative history, or generalized notions of congressional
purposes that are not embodied within the text of federal law”). For further background on the legal debate over using
legislative history and other extratextual evidence to interpret statutes, see CRS Report R45153, Statutory
Interpretation: Theories, Tools, and Trends, by Valerie C. Brannon.
20 The Supreme Court uses the term “police power” to refer to the states’ general power of governing, such as
regulating to promote public health, safety, and welfare. See, e.g., Nat’l Fed’n of Indep. Bus. v. Sebelius, 567 U.S. 519,
536 (2012) (“Our cases refer to this general power of governing, possessed by the States but not by the Federal
Government, as the ‘police power.’”).
21 Rice v. Santa Fe Elevator Corp., 331 U.S. 218, 230 (1947); see also, e.g., Wyeth, 555 U.S. at 565 (“[I]n all pre-
emption cases, and particularly in those in which Congress has legislated . . . in a field which the States have
traditionally occupied, . . . 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.’”) (citations and internal
quotation marks omitted); N.Y. State Conf. of Blue Cross & Blue Shield Plans v. Travelers Ins. Co., 514 U.S. 645, 654
(1995) (“[W]e have never assumed lightly that Congress has derogated state regulation, but instead have addressed
claims of pre-emption with the starting presumption that Congress does not intend to supplant state law.”); Puerto Rico
Dep’t of Consumer Affs. v. Isla Petroleum Corp., 485 U.S. 495, 500 (1988) (“As we have repeatedly stated, 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.”) (citations and internal quotation marks omitted).
22 See Tarrant Reg’l Water Dist. v. Herrmann, 569 U.S. 614, 631 n.10 (2013); Cipollone v. Liggett Grp., Inc., 505 U.S.
504, 533 (1992) (Blackmun, J., concurring in part, concurring in the judgment in part, and dissenting in part).
23 See, e.g., Mut. Pharm. Co. v. Bartlett, 570 U.S. 472 (2013) (holding that federal law preempted state law without
mentioning the presumption against preemption); Kurns v. R.R. Friction Prods. Corp., 565 U.S. 625 (2012) (similar);
PLIVA, Inc. v. Mensing, 564 U.S. 604, 622 (2011) (similar); Bruesewitz v. Wyeth LLC, 562 U.S. 223 (2011) (similar);
Rowe v. New Hampshire Motor Transport Ass’n, 552 U.S. 364 (2008) (similar); Geier v. Am. Honda Motor Co., 529
U.S. 861 (2000) (similar); United States v. Locke, 529 U.S. 89, 108 (2000) (similar). See also, e.g., Charles W. Tyler &
Heather K. Gerken, The Myth of the Laboratories of Democracy, 122 Colum. L. Rev. 2187, 2240 (2022) (“The Court
has recognized the presumption since its 1947 decision in Rice v. Santa Fe Elevator Corp., but it has applied the
presumption only episodically—sometimes calling it a ‘cornerstone[]’ of preemption jurisprudence, other times
ignoring it entirely.”); Thomas W. Merrill, Preemption and Institutional Choice, 102 Nw. U. L. Rev. 727, 741 (2008)
(“[T]he presumption against preemption is honored as much in the breach as in observance.”).
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In a 2016 decision, the Court also appeared to depart from prior case law24 when it suggested that
the presumption did not apply in express preemption cases.25 Since that decision, lower courts
have disagreed over the presumption’s application to interpretations of preemption clauses.26
Although several federal circuit courts have held that the presumption no longer applies in
express preemption cases,27 one circuit court has concluded that the presumption remains valid in
cases involving areas historically regulated by states.28
The Supreme Court has also appeared to endorse a narrower exception to the presumption against
preemption involving areas in which the federal government has traditionally had a “significant”
regulatory presence.29 In United States v. Locke, the Court held that the federal Ports and
Waterways Safety Act preempted state regulations involving maritime commerce—an area in
which there was a “history of significant federal presence.”30 When a state regulates in such an
area, the Court explained, “there is no beginning assumption that concurrent regulation by the
State is a valid exercise of its police powers.”31
In a subsequent decision, however, the Court appeared to retreat from its reasoning in Locke. In
its 2009 decision in Wyeth v. Levine, the Court invoked the presumption when it held that federal
law did not preempt certain state law claims concerning drug labeling.32 In allowing the claims to
proceed, the Court acknowledged that the federal government had regulated drug labeling for
more than a century, but explained that the presumption can apply even when the federal
government has long regulated a subject.33

24 See, e.g., CTS Corp. v. Waldburger, 573 U.S. 1, 19 (2014) (“[W]hen the text of a pre-emption clause is susceptible of
more than one plausible reading, courts ordinarily accept the reading that disfavors preemption.”) (citations and internal
quotation marks omitted); Wyeth, 555 U.S. at 565 (explaining that the presumption against preemption applies “[i]n all
pre-emption cases”); Altria Grp., Inc. v. Good, 555 U.S. 70, 77 (2008) (explaining that the Court “begin[s its] analysis”
with a presumption against preemption “[w]hen addressing questions of express or implied pre-emption”) (emphasis
added); Bates v. Dow Agrosciences LLC, 544 U.S. 431, 449 (2005) (“Even if [the defendant] had offered us a plausible
alternative reading of [the relevant preemption clause]—indeed, even if its alternative were just as plausible as our
reading of the text—we would nevertheless have a duty to accept the reading that disfavors pre-emption.”); Egelhoff v.
Egelhoff ex rel. Breiner, 532 U.S. 141, 151 (2001) (invoking the presumption against preemption in interpreting
ERISA’s preemption clause); Medtronic, Inc. v. Lohr, 518 U.S. 470, 485 (1996) (explaining that the presumption
against preemption applies “[i]n all pre-emption cases”); De Buono v. NYSA-ILA Med. & Clinical Servs. Fund, 520
U.S. 806, 814 (1997) (invoking the presumption against preemption in interpreting ERISA’s preemption clause);
Travelers, 514 U.S. at 654 (same); Cipollone, 505 U.S. at 518 (invoking the presumption against preemption in
interpreting the Federal Cigarette Labeling and Advertising Act’s preemption clause).
25 Puerto Rico v. Franklin Cal. Tax-Free Tr., 579 U.S. 115, 125 (2016).
26 See, e.g., Cal. Rest. Ass’n v. City of Berkeley, No. 21-16278, 2023 WL 2962921, at *9 (9th Cir. Apr. 17, 2023)
(O’Scannlain, J., concurring) (collecting cases and observing that “[t]here is much confusion over how broadly to read
Franklin[]”).
27 See Dialysis Newco, Inc. v. Cmty. Health Sys. Grp. Health Plan, 938 F.3d 246, 259 (5th Cir. 2019); Watson v. Air
Methods Corp., 870 F.3d 812, 817 (8th Cir. 2017); EagleMed LLC v. Cox, 868 F.3d 893, 903 (10th Cir. 2017); Atay v.
Cnty. of Maui, 842 F.3d 688, 699 (9th Cir. 2016).
28 See Lupian v. Joseph Cory Holdings LLC, 905 F.3d 127, 131 n.5 (3d Cir. 2018) (“[W]e have determined that,
because [Franklin] . . . did not address claims involving areas historically regulated by states, we would continue to
apply the presumption against preemption to express preemption claims.”).
29 United States v. Locke, 529 U.S. 89, 108 (2000).
30 Id.
31 Id.
32 Wyeth v. Levine, 555 U.S. 555, 565 n.3 (2009).
33 Id. (explaining that the presumption’s application “accounts for the historic presence of state law but does not rely on
the absence of federal regulation”).
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Whether the presumption continues to apply in fields traditionally regulated by the federal
government thus remains unclear.
Language Commonly Used in Express Preemption
Clauses
Congress often relies on the language of existing preemption clauses in drafting new legislation.34
This type of reliance can have important consequences, as courts often look to the settled
meaning of statutory language to discern Congress’s intent.35
This section of the report discusses how the Supreme Court has interpreted federal statutes that
expressly preempt (1) state laws “related to” certain subjects, (2) state laws concerning certain
subjects “covered” by federal laws and regulations, (3) state requirements that are “in addition to,
or different than” federal requirements, and (4) state “requirements,” “laws,” “regulations,” and
“standards.”36
While preemption decisions depend heavily on the details of particular statutory schemes, the
Court has assigned some of these phrases specific meanings even when they have appeared in
different statutory contexts.
“Related to”
Some preemption clauses provide that a federal statute supersedes all state laws that are “related
to” a specific matter of federal regulatory concern. The Supreme Court has characterized such
provisions as “deliberatively expansive”37 and “conspicuous for [their] breadth.”38
At the same time, the Court has cautioned against strictly literal interpretations of “related to”
preemption clauses. Instead of reading such clauses “to the furthest stretch of [their]

34 ALAN UNTEREINER, THE PREEMPTION DEFENSE IN TORT ACTIONS: LAW, STRATEGY AND PRACTICE 77 (2008)
(“Although express preemption provisions cover a wide range of subjects, they also follow certain familiar patterns.
They often contain similar if not identical words or phrases, including limitations on or exceptions to the scope of
preemption.”).
35 See Bragdon v. Abbott, 524 U.S. 624, 645 (1998) (“When administrative and judicial interpretations have settled the
meaning of an existing statutory provision, repetition of the same language in a new statute indicates, as a general
matter, the intent to incorporate its administrative and judicial interpretations as well.”); see also Morales v. Trans
World Airlines, Inc., 504 U.S. 374, 383–84 (1992) (relying on the Court’s earlier interpretation of a preemption clause
in the Employee Retirement Income Security Act to interpret a similarly worded preemption clause in the Airline
Deregulation Act).
36 Although some preemption clauses might appear to issue commands directly to states, the Supreme Court has
explained that all forms of preemption are based on federal laws that regulate private actors. Murphy v. Nat’l Collegiate
Athletic Ass’n, 138 S. Ct. 1461, 1475, 1479–80 (2018). The Constitution authorizes Congress to “regulate individuals,
not States,” and the Court therefore requires that preemption clauses must be “best read” as conferring rights or
imposing restrictions on private actors. Id. at 1479. For example, the preemption clause in the Airline Deregulation Act
of 1978 provides that “no State . . . shall enact or enforce any law” related to prices, routes, or services of a covered air
carrier. 49 U.S.C. § 41713(b)(1) (as amended). The Court has explained that, while this clause “might appear to operate
directly on States,” it instead regulates private actors by conferring on covered carriers “a federal right to engage in
certain conduct subject only to certain (federal) constraints.” Murphy, 138 S. Ct. at 1480. For a more in-depth
discussion of the relationship between preemption principles and the prohibition on issuing direct commands to states
(the “anticommandeering” doctrine), see CRS Report R45323, Federalism-Based Limitations on Congressional Power:
An Overview, coordinated by Kevin J. Hickey.
37 Pilot Life Ins. Co. v. Dedeaux, 481 U.S. 41, 46 (1987).
38 FMC Corp. v. Holliday, 498 U.S. 52, 58 (1990).
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indeterminacy,”39 the Court has looked to Congress’s statutory objectives to cabin the clauses’
scope.40
The following subsections discuss the Court’s interpretation of three statutes that contain “related
to” preemption clauses: the Employee Retirement Income Security Act, the Airline Deregulation
Act, and the Federal Aviation Administration Authorization Act.
Employee Retirement Income Security Act
The Employee Retirement Income Security Act (ERISA) contains perhaps the most prominent
example of a preemption clause that uses “related to” language.41 ERISA imposes comprehensive
federal regulations on private employee benefit plans.42 The statute also contains a preemption
clause providing that its requirements preempt all state laws that “relate to” regulated benefit
plans.43
In interpreting this provision, the Supreme Court has held that ERISA preempts two categories of
state law: (1) state laws that have a “connection with” ERISA plans, and (2) state laws that
contain a “reference to” ERISA plans.44
The Court has held that state laws have an impermissible “connection with” ERISA plans if they
govern “a central matter of plan administration” or interfere with “nationally uniform plan
administration.”45 In contrast, state laws that indirectly affect ERISA plans are not preempted
unless the relevant effects are particularly “acute.”46
Applying these standards, the Court has ruled that ERISA preempts state laws governing areas of
“core ERISA concern,” like the designation of ERISA plan beneficiaries47 and the disclosure of
information regarding health plan benefits.48
In contrast, the Supreme Court has held that ERISA does not preempt state laws imposing
surcharges on certain types of insurers49 and mandating wage levels for specific categories of
employees who work on public projects.50 The Court has explained that these state laws are

39 N.Y. State Conference of Blue Cross & Blue Shield Plans v. Travelers Ins. Co., 514 U.S. 645, 655 (1995).
40 See, e.g., id. at 656 (“We simply must . . . look instead to the objectives of the . . . statute as a guide to the scope of
the state law that Congress understood would survive.”); Dan’s City Used Cars, Inc. v. Pelkey, 569 U.S. 251, 263–64
(2013); Travelers, 514 U.S. at 661. See also Cal. Div. of Labor Standards Enf’t v. Dillingham Constr., N.A., Inc., 519
U.S. 316, 335 (1997) (Scalia, J., concurring) (“[A]pplying the ‘relate to’ provision [in the Employee Retirement Income
Security Act (ERISA)] according to its terms was a project doomed to failure, since, as many a curbstone philosopher
has observed, everything is related to everything else.”).
41 Daniel J. Meltzer, Preemption and Textualism, 112 MICH. L. REV. 1, 20 (2013) (“The most frequently litigated
‘related to’ preemption clause is found in [ERISA].”).
42 See 29 U.S.C. §§ 1001–1461.
43 Id. § 1144(a).
44 Rutledge v. Pharm. Care Mgmt. Ass’n, 141 S. Ct. 474, 479–81 (2020); Shaw v. Delta Air Lines, Inc., 463 U.S. 85,
96–97 (1983).
45 Rutledge, 141 S. Ct. at 480; Egelhoff v. Egelhoff ex rel. Breiner, 532 U.S. 141, 148 (2001).
46 Travelers, 514 U.S. at 668. See also Rutledge, 141 S. Ct. at 480–81.
47 Egelhoff, 532 U.S. at 147.
48 Gobeille v. Liberty Mut. Ins. Co., 577 U.S. 312, 323 (2016).
49 Travelers, 514 U.S. at 651–52.
50 Cal. Div. of Labor Standards Enf’t v. Dillingham Constr., N.A., Inc., 519 U.S. 316, 334 (1997).
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permissible because they affect ERISA plans only indirectly and that ERISA preempts such laws
only if the relevant indirect effects are particularly strong.51
The Court has also held that ERISA preempts state laws that contain an impermissible “reference
to” ERISA plans. Under the Court’s case law, a state law will contain an impermissible “reference
to” ERISA plans where it “acts immediately and exclusively upon ERISA plans,” or where the
existence of an ERISA plan is “essential” to the state law’s operation.52
In Mackey v. Lanier Collection Agency & Service, Inc., for example, the Supreme Court
concluded that ERISA preempted a state statute that prohibited the garnishment of funds in plans
“subject to . . . [ERISA].”53 Because the challenged state statute expressly referenced ERISA
plans, the Court held that it fell within the scope of ERISA’s preemption clause even if it was
enacted “to help effectuate ERISA’s underlying purposes.”54
Similarly, in Ingersoll-Rand Company v. McClendon, the Court held that ERISA preempted an
employee’s state law claim alleging that he was terminated in order to prevent his regulated
pension from vesting.55 The Court reasoned that ERISA preempted this state law claim because
the action made specific reference to and was premised on the existence of an ERISA-regulated
pension plan.56
The Supreme Court’s decision in District of Columbia v. Greater Washington Board of Trade
offers a third example of preemption based on a state law’s “reference to” ERISA plans.57 There,
the Court held that ERISA preempted a state statute requiring employers that provided health
insurance to their employees to continue providing coverage at existing benefit levels while
employees received workers’ compensation benefits.58 This state law was preempted, the Court
concluded, because ERISA regulates employee health insurance, meaning that the state law
specifically referred to ERISA-regulated plans.59
Airline Deregulation Act
The Airline Deregulation Act (ADA) is another example of a statute that employs “related to”
preemption language.60 Enacted in 1978, the ADA largely deregulated domestic air
transportation.61
To ensure that state governments did not interfere with this deregulatory effort, the ADA prohibits
states from enacting laws “related to a price, route, or service of an air carrier.”62

51 Travelers, 514 U.S. at 668. See also Rutledge, 141 S. Ct. at 480 (“A state law may . . . be subject to pre-emption if
acute, albeit indirect, economic effects of the state law force an ERISA plan to adopt a certain scheme of substantive
coverage.”) (internal quotation marks omitted).
52 Dillingham, 519 U.S. at 325.
53 486 U.S. 825, 828 (1988) (quoting Ga. Code Ann. § 18-4-22.1 (1982)).
54 Id. at 829–30.
55 498 U.S. 133, 139–41 (1990).
56 Id. at 140.
57 506 U.S. 125 (1992).
58 Id. at 130.
59 Id.
60 49 U.S.C. § 1371 (1979).
61 Am. Airlines, Inc. v. Wolens, 513 U.S. 219, 222 (1995).
62 49 U.S.C. § 41713(b)(1) (as amended) (emphasis added).
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In interpreting this language, the Supreme Court has relied upon similar reasoning as used in its
ERISA decisions, concluding that the ADA preempts state laws that have a “connection with” or
“reference to” airline prices, routes, or services.63
In Morales v. Trans World Airlines, Inc., for example, the Court relied in part on its ERISA case
law to hold that the ADA preempted a state’s effort to enforce guidelines regarding the content
and format of airline fare advertising.64 The Court reached this conclusion on the grounds that the
guidelines expressly referenced airfares and were likely to have a significant impact on airfares.65
Federal Aviation Administration Authorization Act
The Federal Aviation Administration Authorization Act of 1994 (FAAA) is a third example of a
statute that utilizes “related to” preemption language.66 While the FAAA is (as its title suggests)
principally concerned with aviation regulation, it also supplemented Congress’s deregulation of
the trucking industry. The statute pursued this objective with a preemption clause prohibiting
states from enacting laws “related to a price, route, or service of any motor carrier . . . with
respect to the transportation of property.”67
In Rowe v. New Hampshire Motor Transport Association, the Supreme Court relied in part on its
ERISA and ADA case law to hold that the FAAA preempted certain state laws regulating the
delivery of tobacco, including a law that required retailers shipping tobacco to employ motor
carriers that utilized certain kinds of recipient-verification services.68
The Court reached this conclusion for two principal reasons. First, the Court reasoned that the
requirement had an impermissible “connection with” motor carrier services because it “focuse[d]
on” such services.69 Second, the Court concluded that the FAAA preempted the state law because
of the state law’s significant adverse effects on the federal statute’s deregulatory objectives.
Specifically, the Court reasoned that the state law had a “connection with” these objectives
because it dictated that motor carriers use certain types of recipient-verification services, thereby
substituting the state’s commands for competitive market forces.70
Although the Supreme Court has thus relied on its ERISA and ADA case law in interpreting the
FAAA’s preemption clause, the Court has also explained that the clause’s “with respect to”
qualifying language significantly narrows the statute’s preemptive scope.
In Dan’s City Used Cars, Inc. v. Pelkey, the Court relied on this language to hold that the FAAA
did not preempt state law claims involving the storage and disposal of a towed car.71 In allowing
the claims to proceed, the Court observed that the FAAA’s preemption clause mirrored the ADA’s
preemption clause with “one conspicuous alteration”—the addition of the phrase “with respect to

63 Morales v. Trans World Airlines, Inc., 504 U.S. 374, 384 (1992) (“Since the relevant language of the ADA is
identical, we think it appropriate to adopt the same standard here: State enforcement actions having a connection with
or reference to airline ‘rates, routes, or services’ are pre-empted . . . .”).
64 Id. at 388–89.
65 Id. at 390; see id. at 388 (“[B]eyond the guidelines’ express reference to fares, it is clear as an economic matter that
state restrictions on fare advertising have the forbidden significant effect upon fares.”).
66 49 U.S.C. § 14501.
67 Id. § 14501(c)(1) (emphasis added).
68 552 U.S. 364, 368 (2008).
69 Id. at 371.
70 Id. at 372.
71 569 U.S. 251, 265 (2013).
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the transportation of property.”72 According to the Court, this phrase “massively” limited the
scope of FAAA preemption.73 Because the relevant state law claims involved the storage and
disposal of towed vehicles rather than their transportation, the Court held that they did not qualify
as state laws that “related to” motor carrier services “with respect to the transportation of
property.”74
Takeaways
The Supreme Court’s case law concerning “related to” preemption clauses reflects a number of
general principles. The Court has consistently held that state laws “relate to” matters of federal
regulatory concern when they have a “connection with” or contain a “reference to” such
matters.75
Generally, state laws have an impermissible “connection with” matters of federal concern when
they:
• prescribe rules governing an issue central to the relevant federal regulatory
scheme;76
• interfere with uniform national policies regarding a matter of federal concern;77
or
• have indirect effects on the federal scheme that are particularly “acute”78 or
“significant.”79
As a corollary to the latter principle, the Court has made clear that state laws having only
“tenuous, remote, or peripheral” effects on an issue of federal concern are not sufficiently “related
to” the issue to warrant preemption.80
The Court has concluded that state laws contain a “reference to” a matter of federal regulatory
interest if they “act[] immediately and exclusively upon” the matter or if the existence of a federal
regulatory scheme is “essential” to the state law’s operation.81
The inclusion of qualifying language can narrow the scope of “related to” preemption clauses. As
the Court made clear in Dan’s City, the scope of “related to” preemption clauses can be
significantly limited by the addition of “with respect to” qualifying language.82

72 Id. at 261.
73 Id. (citation and internal quotation marks omitted).
74 Id. (emphasis added).
75 See, e.g., Rutledge v. Pharm. Care Mgmt. Ass’n, 141 S. Ct. 474, 479 (2020); Rowe v. N.H. Motor Transport Ass’n,
552 U.S. 364, 370 (2008); Morales v. Trans World Airlines, Inc., 504 U.S. 374, 383 (1992); Shaw v. Delta Air Lines,
Inc., 463 U.S. 85, 96 (1983).
76 Egelhoff v. Egelhoff ex rel. Breiner, 532 U.S. 141, 148 (2001).
77 Rutledge, 141 S. Ct. at 479–81.
78 N.Y. State Conf. of Blue Cross & Blue Shield Plans v. Travelers Ins. Co., 514 U.S. 645, 668 (1995).
79 Morales, 504 U.S. at 388.
80 Shaw, 463 U.S. at 100 n.21.
81 Cal. Div. of Labor Standards Enf’t v. Dillingham Constr., N.A., Inc., 519 U.S. 316, 325 (1997).
82 Dan’s City Used Cars, Inc. v. Pelkey, 569 U.S. 251, 261 (2013).
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“Covering”
The Federal Railroad Safety Act contains a preemption clause allowing states to regulate railroad
safety until the federal government prescribes a regulation or issues an order “covering the
subject matter” of the relevant state requirement.83
In CSX Transportation, Inc. v. Easterwood, the Supreme Court interpreted this language as
having a narrower effect than “related to” preemption clauses.84 The Court explained that
“covering” is a more restrictive term than “related to,” and that federal law will accordingly cover
the subject of a state law only if it “substantially subsume[s]” that subject.85
Applying this standard, the Court held that federal regulations of grade crossing safety did not
preempt state law claims alleging that a train operator failed to maintain adequate warning
devices at a crossing where a collision had occurred.86 The Court allowed these claims to proceed
because the relevant federal regulations did not “substantially subsume” the subject of warning
device adequacy.87
At the same time, the Easterwood Court held that federal regulations preempted other state law
claims alleging that a train traveled at an unsafe speed. In holding that these claims were
preempted, the Court reasoned that federal maximum-speed regulations “substantially
subsumed”—and therefore “covered”—the subject of train speeds.88
“In addition to, or different than”
A number of federal statutes preempt state requirements that are “in addition to, or different than”
federal requirements.89 The Supreme Court has explained that these statutes preempt state law
even in cases where a regulated entity can comply with both federal and state requirements.
The Court adopted this position in National Meat Association v. Harris, where it interpreted a
preemption clause in the Federal Meat Inspection Act (FMIA) prohibiting states from imposing

83 49 U.S.C. § 20106(a)(2).
84 507 U.S. 658, 664 (1993).
85 Id.
86 Id. at 665–73.
87 Id. at 667. The Court held that related regulations concerning warning devices installed with federal funds did not
apply to the facts in Easterwood. Id. at 670–73. The Court later held that federal law and these regulations preempted
state law claims against a train operator for the alleged inadequacy of warning devices installed using federal funds.
Norfolk S. Ry. Co. v. Shanklin, 529 U.S. 344, 358–59 (2000).
88 507 U.S. at 673–76.
89 See, e.g., 7 U.S.C. § 136v(b) (providing that states “shall not impose or continue in effect any requirements for
labeling and packaging [pesticides] in addition to or different from those required under this subchapter”) (emphasis
added); 21 U.S.C. § 467e (“Marking, labeling, packaging, or ingredient requirements . . . in addition to, or different
than, those made under this chapter may not be imposed by any State . . . .”) (emphasis added); 7 U.S.C. § 4817(b)
(“The regulation of [promotion and consumer education involving pork and pork products] . . . that is in addition to or
different from this chapter may not be imposed by a State.”) (emphasis added); 21 U.S.C. § 360k(a) (“[N]o state . . .
may establish or continue in effect with respect to a device intended for human use any requirement . . . which is
different from, or in addition to, any requirement applicable under this chapter to the device, and . . . which relates to
the safety or effectiveness of the device or to any other matter included in a requirement applicable to the device under
this chapter.”) (emphasis added); 21 U.S.C. § 1052(b) (“Requirements within the scope of this chapter with respect to
premises, facilities, and operations of any official plant which are in addition to or different than those made under this
chapter may not be imposed by any State . . . .”) (emphasis added).
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requirements on meatpackers and slaughterhouses that are “in addition to, or different than”
federal requirements.90
In Harris, the Court held that certain California slaughterhouse regulations were “in addition to,
or different than” federal regulations because they imposed a distinct set of requirements that
went beyond those imposed by federal law.91 Because the California requirements differed from
federal requirements, the Court explained, they fell within the plain meaning of the FMIA’s
preemption clause, even though slaughterhouses were able to comply with both sets of
restrictions.92
Preemption clauses that employ “in addition to, or different than” language often raise a second
interpretive issue involving the status of state requirements that are identical to federal
requirements.
The Supreme Court has interpreted two statutes employing this language to not preempt parallel
state law requirements.93 In instructing lower courts on how to assess whether state requirements
in fact parallel federal requirements, the Court has explained that state law need not explicitly
incorporate federal standards in order to avoid qualifying as “in addition to, or different than”
federal requirements.94 Instead, the relevant inquiry looks to the substance of state requirements
to determine whether they mirror federal law.
The Court has also explained that state requirements do not qualify as “in addition to, or different
than” federal requirements simply because state law provides injured plaintiffs with different
remedies than federal law.95 Accordingly, absent contextual evidence to the contrary, preemption
clauses that employ “in addition to, or different than” language will allow states to give plaintiffs
a damages remedy for violations of state requirements even where federal law does not offer such
a remedy for violations of parallel federal requirements.96
“Requirements,” “Laws,” “Regulations,” and “Standards”
Federal statutes frequently preempt state “requirements,” “laws,” “regulations,” and/or
“standards” concerning subjects of federal regulatory concern.97 These preemption clauses have
raised the question of whether they encompass state common law actions.

90 565 U.S. 452, 455 (2012).
91 Id. at 459 (citation and internal quotation marks omitted).
92 Id. at 459–60.
93 Bates v. Dow Agrosciences LLC, 544 U.S. 431, 446 (2005); Medtronic, Inc. v. Lohr, 518 U.S. 470, 494–97 (1996).
94 Bates, 544 U.S. at 447.
95 See id. at 447–48.
96 See id.
97 See, e.g., 7 U.S.C. § 136v(b) (providing that no state “shall . . . impose or continue in effect any requirements for
labeling or packaging in addition to or different from those required under this subchapter”) (emphasis added); 21
U.S.C. § 360k(a) (providing that no state “may establish or continue in effect with respect to a device intended for
human use any requirement . . . which is different from, or in addition to, any requirement applicable under this chapter
to the device”) (emphasis added); 46 U.S.C. § 4306 (“[A] State . . . may not establish, continue in effect, or enforce a
law or regulation establishing a recreational vessel or associated equipment performance or other safety standard or
imposing a requirement for associated equipment . . . that is not identical to a regulation prescribed under . . . this
title.”) (emphasis added); 49 U.S.C. § 30103(b)(1) (“When a motor vehicle safety standard is in effect under this
chapter, a State . . . may prescribe or continue in effect a standard applicable to the same aspect of performance of a
motor vehicle or motor vehicle equipment only if the standard is identical to the standard prescribed under this
chapter.”) (emphases added).
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The Supreme Court has explained that, absent evidence to the contrary, a preemption clause’s
reference to state “requirements” includes state common law duties.98
In contrast, the Court has interpreted one preemption clause’s reference to state “law[s] or
regulation[s]” as encompassing only “positive enactments” and not common law actions.99 The
Court reached this conclusion in Sprietsma v. Mercury Marine, where it held that the Federal Boat
Safety Act of 1971 (FBSA) did not preempt common law claims involving boat safety.100 The
FBSA contains a preemption clause prohibiting states from enforcing “a law or regulation”
concerning boat safety that is not identical to federal laws and regulations.101 The statute also
includes a savings clause providing that compliance with federal requirements does not “relieve a
person from liability at common law or under State law.”102
In Sprietsma, the Court held that the phrase “law or regulation” in the FBSA’s preemption clause
did not encompass state common law claims for three reasons.103 First, the Court reasoned that
the inclusion of the article “a” before “law or regulation” implied a “discreteness” that is reflected
in statutes and regulations, but not in common law.104 Second, the Court concluded that the
pairing of the terms “law” and “regulation” indicated that Congress intended to preempt only
positive enactments. In particular, the Court reasoned that if the term “law” were given an
expansive interpretation that included common law claims, it would also encompass “regulations”
and thereby render the inclusion of that latter term superfluous.105 Third, the Court reasoned that
the FBSA’s savings clause provided additional support for the conclusion that the phrase “law or
regulation” did not encompass common law actions.106
With respect to federal statutes that preempt state “standards,” the Supreme Court has explained
that it is possible to interpret “standards” as encompassing common law actions, but it has
interpreted the term more narrowly where the specific statutory context suggested that Congress
did not intend to preempt common-law tort actions.107
Savings Clauses
Many federal statutes contain provisions that purport to restrict their preemptive effect. These
savings clauses make clear that federal law does not preempt certain categories of state law,
reflecting Congress’s recognition of the need for states to “fill a regulatory void” or “enhance
protection for affected communities” through supplementary regulation.108

98 Riegel v. Medtronic, Inc., 552 U.S. 312, 324 (2008); see also Medtronic, Inc. v. Lohr, 518 U.S. 470 (1996);
Cipollone v. Liggett Grp., Inc., 505 U.S. 504, 521 (1992).
99 Sprietsma v. Mercury Marine, 537 U.S. 51, 63 (2002).
100 Id.
101 46 U.S.C. § 4306.
102 Id. § 4311(h).
103 Sprietsma, 537 U.S. at 63.
104 Id.
105 Id.
106 Id.
107 Geier v. Am. Honda Motor Co., 529 U.S. 861, 868 (2000). For a further discussion of the Court’s holding in Geier,
see infra “Compliance Savings Clauses.”
108 Sandi Zellmer, When Congress Goes Unheard: Savings Clauses’ Rocky Judicial Reception, in PREEMPTION CHOICE:
THE THEORY, LAW, AND REALITY OF FEDERALISM’S CORE QUESTION 144, 146 (William W. Buzbee ed., 2009).
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The law regarding savings clauses “is not especially well developed,” and cases involving such
clauses “turn very much on the precise wording of the statutes at issue.”109
With these caveats in mind, this section discusses three general categories of savings clauses: (1)
“anti-preemption provisions,” (2) “compliance savings clauses,” and (3) “remedies savings
clauses.”
Anti-Preemption Provisions
Some savings clauses contain language indicating that “nothing in” the relevant federal statute
“may be construed to preempt or supersede” certain categories of state law.110 Others say that the
relevant federal statute “does not annul, alter, or affect” state laws “except to the extent that those
laws are inconsistent” with the federal statute.111 Certain statutes containing this “inconsistency”
language further provide that state laws are not “inconsistent” with the relevant federal statute if
they provide greater protection to consumers than federal law.112 Some courts and commentators
have labeled these clauses “anti-preemption provisions.”113
Courts have given effect to the plain language of these provisions, concluding that they evince
Congress’s intent to allow states to adopt regulations that are consistent with federal law.114

109 UNTEREINER, supra note 34, at 204–05.
110 See, e.g., 7 U.S.C. § 2910(a) (“Nothing in this chapter may be construed to preempt or supersede any other program
relating to beef promotion organized and operated under the laws of the United States or any State.”); id. § 6812(c)
(“Nothing in this chapter may be construed to preempt or supersede any other program relating to cut flowers or cut
greens promotion and consumer information organized and operated under the laws of the United States or a State.”);
id. § 7811(c) (“Nothing in this chapter may be construed to preempt or supersede any other program relating to Hass
avocado promotion, research, industry information, and consumer information organized and operated under the laws
of the United States or of a State.”).
111 See, e.g., 12 U.S.C. § 2616 (“This chapter does not annul, alter, or affect, or exempt any person subject to the
provisions of this chapter from complying with, the laws of any State with respect to [real estate] settlement practices,
except to the extent that those laws are inconsistent with any provision of this chapter, and then only to the extent of the
inconsistency.”); 15 U.S.C. § 1693q (“This subchapter does not annul, alter, or affect the laws of any State relating to
electronic fund transfers, dormancy fees, inactivity charges or fees, service fees, or expiration dates of gift certificates,
store gift cards, or general-use prepaid cards, except to the extent that those laws are inconsistent with the provisions of
this subchapter, and then only to the extent of the inconsistency.”); 15 U.S.C. § 5722(a) (“This subchapter does not
annul, alter, or affect, or exempt any person subject to the provisions of this subchapter from complying with, the laws
of any State with respect to telephone billing practices, except to the extent that those laws are inconsistent with any
provision of this subchapter, and then only to the extent of the inconsistency.”).
112 12 U.S.C. § 2616 (authorizing the Consumer Financial Protection Bureau (CFPB) to determine whether state laws
are “inconsistent with” the relevant federal statute, and providing that the CFPB “may not determine that any State law
is inconsistent with” the federal statute “if the [CFPB] determines that such law gives greater protection to the
consumer.”); 15 U.S.C. § 1693q (“A State law is not inconsistent with this subchapter if the protection such law affords
any consumer is greater than the protection afforded by this subchapter.”); 15 U.S.C. § 5722(a) (authorizing the Federal
Trade Commission (FTC) to determine whether state laws are “inconsistent with” the relevant federal statute, and
providing that the FTC “may not determine that any State law is inconsistent with” the federal statute “if the [FTC]
determines that such law gives greater protection to the consumer.”).
113 See Gobeille v. Liberty Mut. Ins. Co., 577 U.S. 312, 326 (2016); Bank of Am. v. City & Cnty. of S.F., 309 F.3d 551,
565 (9th Cir. 2002); Bank One v. Guttau, 190 F.3d 844, 850 (8th Cir. 1999); UNTEREINER, supra note 34, at 20.
114 See, e.g., Perkins v. Johnson, 551 F. Supp. 2d 1246, 1255 (D. Colo. 2008).
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Compliance Savings Clauses
Some savings clauses provide that compliance with federal law does not relieve a person from
liability under state law.115 The principal interpretive issue with such clauses is whether they limit
a statute’s preemptive effect (a question of federal law) or are instead intended to discourage the
conclusion that compliance with federal regulations necessarily renders a product nondefective as
a matter of state tort law.116
While the Supreme Court has not adopted a generally applicable rule concerning the meaning of
compliance savings clauses, it has concluded that such clauses can support a narrow interpretation
of a statute’s preemptive effect.
In Geier v. American Honda Motor Co., the Court relied in part on a compliance savings clause in
the National Traffic and Motor Vehicle Safety Act (NTMVSA) to hold that the statute did not
expressly preempt state common law claims against an automobile manufacturer.117 The
NTMVSA contains a preemption clause prohibiting states from enforcing safety standards for
motor vehicles that are not identical to federal standards.118 The statute also includes a savings
clause providing that compliance with federal safety standards does not “exempt any person from
any liability under common law.”119
In Geier, the Court explained that, although it was “possible” to read the NTMVSA’s preemption
clause standing alone as encompassing the state law claims, that reading of the statute would
leave the Act’s savings clause without effect.120 The Court thus held that the NTMVSA did not
expressly preempt state common law claims based in part on the Act’s savings clause.121
Similarly, as discussed, the Court’s decision in Sprietsma v. Mercury Marine indicated that a
compliance savings clause in the FBSA “buttresse[d]” the conclusion that state common law
claims did not qualify as “law[s] or regulation[s]” within the meaning of the statute’s preemption
clause.122

115 See, e.g., 15 U.S.C. § 2074(a) (“Compliance with consumer product safety rules or other rules or orders under this
chapter shall not relieve any person from liability at common law or under State statutory law to any other person.”); 21
U.S.C. § 360pp(e) (“Except as provided in the first sentence of section 360ss of this title, compliance with this part or
any regulations issued thereunder shall not relieve any person from liability at common law or under statutory law.”);
42 U.S.C. § 5409(c) (“Compliance with any Federal manufactured home construction or safety standard issued under
this chapter does not exempt any person from any liability under common law.”); 46 U.S.C. § 4311(h) (providing that
compliance with federal boat regulations “does not relieve a person from liability at common law or under State law.”).
116 See UNTEREINER, supra note 34, at 194–96. In many jurisdictions, a defendant’s compliance with government
regulations can serve as relevant evidence in products liability litigation, and some courts have further held that
compliance with government regulations renders a product nondefective as a matter of law. See RESTATEMENT (THIRD)
OF TORTS: PRODUCTS LIABILITY § 4 cmt. e (1998).
117 529 U.S. 861, 868 (2000).
118 49 U.S.C. § 30103(b). The NTMVSA was recodified without substantive change in 1994, but in Geier the Court
referred to the pre-1994 version of the statute. 529 U.S. at 865; 15 U.S.C. § 1392(d) (1988).
119 49 U.S.C. § 30103(e); 15 U.S.C. § 1397(k) (1988).
120 Geier, 529 U.S. at 868. As discussed in “Automobile Safety Regulations,” the Geier Court held that the NTMVSA
impliedly preempted the relevant common law claims even though it did not expressly preempt those claims. Notably,
the Court appeared to consider the NTMVSA’s savings clause to be relevant only to its interpretation of the statute’s
express preemption clause, reasoning that the savings clause did not create any sort of “special burden” disfavoring
implied preemption. Geier, 529 U.S. at 870–71.
121 Id. at 868.
122 537 U.S. 51, 63 (2002).
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The Court has thus relied on compliance savings clauses to inform its interpretation of
preemption clauses, but has not held that such clauses automatically insulate state laws from
preemption.
Remedies Savings Clauses
Some savings clauses provide that “nothing in” a federal statute “shall in any way abridge or alter
the remedies now existing at common law or by statute.”123 While the case law on these
“remedies savings clauses” is limited, the Supreme Court has interpreted one such clause as
evincing Congress’s intent to disavow field preemption, but not as preserving state laws that
conflict with federal objectives.124
“State” vs. “State or Political Subdivision Thereof”
Some savings clauses limit a federal statute’s preemptive effect with respect to certain laws
enacted by “State[s] or political subdivisions thereof,”125 while others by their terms insulate only
“State” laws.126

123 47 U.S.C. § 414. See also 7 U.S.C. § 209(b) (“[T]his section shall not in any way abridge or alter the remedies now
existing at common law or by statute, but the provisions of this chapter are in addition to such remedies.”); id.
§ 499e(b) (“[T]his section shall not in any way abridge or alter the remedies now existing at common law or by statute,
and the provisions of this chapter are in addition to such remedies.”).
124 See Pennsylvania R.R. v. Puritan Coal Mining Co., 237 U.S. 121, 129–30 (1915) (“The [savings clause] was added
. . . not to nullify other parts of the act, or to defeat rights or remedies given by preceding sections, but to preserve all
existing rights which were not inconsistent with those created by the statute . . . But for this proviso . . . , it might have
been claimed that, Congress having entered the field, the whole subject of liability of carrier to shippers in interstate
commerce had been withdrawn from the jurisdiction of the state courts, and this clause was added to indicate that the
commerce act, in giving rights of action in Federal courts, was not intended to deprive the state courts of their general
and concurrent jurisdiction.”); see also Am. Tel. & Tel. Co. v. Cent. Off. Tel., Inc., 524 U.S. 214, 226 (1998) (holding
that a remedies savings clause in the Communications Act of 1934 did not save state laws that were inconsistent with
federal law).
125 See, e.g., 33 U.S.C. § 1370 (“[N]othing in this chapter shall . . . preclude or deny the right of any State or political
subdivision thereof . . . to adopt or enforce . . . any standard or limitation respecting discharges of pollutants. . . .”)
(emphasis added); 42 U.S.C. § 2018 (“Nothing in this chapter shall be construed to affect the authority or regulations of
any Federal, State, or local agency with respect to the generation, sale, or transmission of electric power produced
through the use of nuclear facilities licensed by the Commission.”) (emphasis added); 42 U.S.C. § 6929 (“Nothing in
this chapter shall be construed to prohibit any State or political subdivision thereof from imposing any requirements,
including those for site selection, which are more stringent than those imposed by such regulations.”) (emphasis
added).
126 See, e.g., 7 U.S.C. § 136v(a) (“A State may regulate the sale or use of any federally registered pesticide or device in
the State, but only if and to the extent that the regulation does not permit any sale or use prohibited by this
subchapter.”) (emphasis added); 42 U.S.C. § 9614(a) (“Nothing in this chapter shall be construed or interpreted as
preempting any State from imposing additional liability or requirements with respect to the release of hazardous
substances within such State.”) (emphasis added); 49 U.S.C. § 14501(c)(2)(A) (providing that the Interstate Commerce
Act “shall not restrict the safety regulatory authority of a State with respect to motor vehicles . . . .”) (emphasis added).
Similarly, some preemption clauses bar any “State or . . . political subdivision thereof” from regulating a certain subject
matter, while others by their terms preempt only “State” laws. Compare 42 U.S.C. § 7543(a) (“No State or any political
subdivision thereof shall adopt or attempt to enforce any standard relating to the control of emissions from new motor
vehicles or new motor vehicle engines subject to this part.”) (emphasis added); 49 U.S.C. § 5125(a) (providing that “a
requirement of a State, political subdivision of a State, or Indian tribe is preempted” under certain circumstances)
(emphasis added); 49 U.S.C. § 14501(a)(1) (“No State or political subdivision thereof . . . shall enact or enforce any
law, rule, regulation, standard, or other provision having the force and effect of law relating to” certain subjects)
(emphasis added), with 7 U.S.C. § 136v(b) (“Such State shall not impose or continue in effect any requirements for
labeling or packaging in addition to or different from those required under this subchapter.”) (emphasis added); 21
(continued...)
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The Supreme Court has twice held that savings clauses that by their terms applied only to “State”
laws also insulated local laws from preemption.
In Wisconsin Public Intervenor v. Mortier, the Court held that the Federal Insecticide, Fungicide,
and Rodenticide Act did not preempt local ordinances regulating pesticides based in part on a
savings clause providing that “State[s]” may regulate federally registered pesticides in certain
circumstances.127 In concluding that the term “State” included political subdivisions of states, the
Court relied on the principle that local governments are “convenient agencies” by which state
governments can exercise their powers.128
Similarly, in City of Columbus v. Ours Garage & Wrecker Service, Inc., the Court held that the
Interstate Commerce Act (ICA) did not preempt municipal safety regulations governing tow-truck
operators based in part on a savings clause providing that the ICA “shall not restrict the safety
regulatory authority of a State with respect to motor vehicles.”129 Relying in part on its reasoning
in Mortier, the Court explained that, absent a clear statement to the contrary, Congress’s reference
to the regulatory authority of a “State” should be read to preserve “the traditional prerogative of
the States to delegate their authority to their constituent parts.”130
Implied Preemption
As discussed, federal law can impliedly preempt state law even when it does not do so
expressly.131 Like its express preemption decisions, the Supreme Court’s implied preemption
cases focus on Congress’s intent.132
The Supreme Court has recognized two general forms of implied preemption: field preemption
and conflict preemption. Field preemption occurs when a pervasive scheme of federal regulation
implicitly precludes supplementary state regulation or when states attempt to regulate a field
where there is a sufficiently dominant federal interest.133 Conflict preemption occurs when state
law interferes with federal goals.134

U.S.C. § 360eee-4(b)(2) (“No State shall regulate third-party logistics providers as wholesale distributors.”) (emphasis
added); 42 U.S.C. § 7543(a) (“No State shall require certification, inspection, or any other approval relating to the
control of emissions from any new motor vehicle or new motor vehicle engine as condition precedent to the initial
retail sale, titling (if any), or registration of such motor vehicle, motor vehicle engine, or equipment.”) (emphasis
added).
127 501 U.S. 597, 607–08 (1991); 7 U.S.C. § 136v(a).
128 Mortier, 501 U.S. at 607–08 (citation and internal quotation marks omitted).
129 536 U.S. 424, 428–29 (2002); 49 U.S.C. § 14501(c)(2)(A).
130 Ours Garage, 536 U.S. at 429.
131 See Crosby v. Nat’l Foreign Trade Council, 530 U.S. 363, 372 (2000).
132 See Wyeth v. Levine, 555 U.S. 555, 565 (2009) (“[T]he purpose of Congress is the ultimate touchstone in every pre-
emption case.”) (quoting Medtronic, Inc. v. Lohr, 518 U.S. 470, 485 (1996)); Retail Clerks Int’l Ass’n v.
Schermerhorn, 375 U.S. 96, 103 (1963)); Barnett Bank of Marion Cnty., N.A. v. Nelson, 517 U.S. 25, 31 (1996)
(explaining that where “explicit pre-emption language does not appear, or does not directly answer the question . . .
courts must consider whether the federal statute’s ‘structure and purpose,’ or nonspecific statutory language,
nonetheless reveal a clear, but implicit, pre-emptive intent.”).
133 See Arizona v. United States, 567 U.S. 387, 399 (2012); Gade v. Nat’l Solid Wastes Mgmt. Ass’n, 505 U.S. 88, 98
(1992).
134 Arizona, 567 U.S. at 399; Gade, 505 U.S. at 98. The Court has explained that these subcategories of implied
preemption are not “rigidly distinct,” and that “field preemption may be understood as a species of conflict preemption”
because “[a] state law that falls within a pre-empted field conflicts with Congress’ intent . . . to exclude state
regulation.” English v. Gen. Elec. Co., 496 U.S. 72, 79 n.5 (1990); see also LAURENCE TRIBE, AMERICAN
(continued...)
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Field Preemption
The Supreme Court has held that federal law preempts state law where Congress has manifested
an intention that the federal government occupy an entire field of regulation.135 Federal law may
reflect such an intent through a scheme of federal regulation that is “so pervasive as to make
reasonable the inference that Congress left no room for States to supplement it,” or where federal
law concerns “a field in which the federal interest is so dominant that the federal system will be
assumed to preclude enforcement of state laws on the same subject.”136
Applying these principles, the Court has held that federal law occupies a variety of regulatory
fields, including alien registration;137 nuclear safety;138 aircraft noise;139 the “design, construction,
alteration, repair, maintenance, operation, equipping, personnel qualification, and manning” of
tanker vessels;140 wholesales of natural gas in interstate commerce;141 and locomotive
equipment.142
Examples
Grain Warehousing
In its 1947 decision in Rice v. Santa Fe Elevator Corp., the Supreme Court held that federal law
preempted a number of fields related to grain warehousing, precluding even complementary state
regulations of those fields.143 In that case, the Court held that the federal Warehouse Act and
associated regulations preempted a variety of state law claims brought against a grain warehouse,
including allegations that the warehouse had engaged in unfair pricing, maintained unsafe
elevators, and impermissibly mixed different qualities of grain.144
The Court discerned Congress’s intent to occupy the relevant fields from an amendment to the
Warehouse Act that made the Secretary of Agriculture’s authorities “exclusive” vis-à-vis federally
licensed warehouses.145 Because the text and legislative history of this amendment reflected
Congress’s intent to eliminate overlapping federal and state warehouse regulations, the Court held
that federal law occupied a number of fields involving grain warehousing. As a result, the Court

CONSTITUTIONAL LAW § 6-29, at 1185 (3d ed. 2000) (noting that when state law “undermines a congressional decision
in favor of national uniformity of standards,” it presents “a situation similar in practical effect to that of federal
occupation of a field”).
135 Arizona, 567 U.S. at 399; Rice v. Santa Fe Elevator Corp., 331 U.S. 218, 230 (1947).
136 Rice, 331 U.S. at 230.
137 See Arizona v. United States, 567 U.S. 387, 401 (2012).
138 See, e.g., English v. Gen. Elec. Co., 496 U.S. 72, 82–85 (1990).
139 City of Burbank v. Lockheed Air Terminal Inc., 411 U.S. 624, 633 (1973).
140 United States v. Locke, 529 U.S. 89, 111 (2000) (quoting 46 U.S.C. § 3703(a)); see Ray v. Atl. Richfield Co., 435
U.S. 151, 163–65 (1978).
141 Schneidewind v. ANR Pipeline Co., 485 U.S. 293, 300, 305 (1988); Exxon Corp. v. Eagerton, 462 U.S. 176, 184
(1983).
142 Kurns v. R.R. Friction Prods. Corp., 565 U.S. 625, 636 (2012).
143 331 U.S. 218 (1947). The Supreme Court’s mid-century decisions did not always clearly distinguish between field
preemption and conflict preemption. See, e.g., Pennsylvania v. Nelson, 350 U.S. 497, 501–02 (1956) (noting that
“different criteria have furnished touchstones” for the Court’s implied preemption decisions, and that the Court had
used a variety of expressions in those decisions, including “conflicting; contrary to; occupying the field; repugnance;
difference; irreconcilability; inconsistency; violation; curtailment; and interference”).
144 Rice, 331 U.S. at 221–22.
145 Id. at 232–33.
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concluded that the Warehouse Act preempted certain state law claims that intruded into those
federally regulated fields, even if federal law established standards that were less strict than those
imposed by state law.146
Immigration: Alien Registration
The Court has also held that federal law preempts the field of alien registration.147 In its 1941
decision in Hines v. Davidowitz, the Court held that federal immigration law—which required
aliens to register with the federal government—preempted a Pennsylvania law that required aliens
to register with the state, pay a registration fee, and carry an identification card.148 The Court
explained that alien regulation is “intimately blended and intertwined” with the federal
government’s core responsibilities and that Congress had enacted a “complete” regulatory scheme
involving that field, meaning federal law preempted the additional state requirements.149
The Court reaffirmed these general principles in its 2012 decision in Arizona v. United States.150
In Arizona, the Court held that the Immigration and Nationality Act (INA), which requires aliens
to carry an alien registration document,151 preempted an Arizona statute that made violations of
that federal requirement a crime under state law.152
In holding that federal law preempted this Arizona requirement, the Court explained that—like
the statutory framework at issue in Hines—the INA represented a “comprehensive” regulatory
regime that occupied the field of alien registration.153 The Court inferred Congress’s intent to
occupy this field from the INA’s “full set of standards” governing alien registration, which
included specific penalties for noncompliance.154 The Court thus held that federal law preempted
even complementary state laws regulating alien registration, like the challenged Arizona
requirement.155
The Court has also made clear, however, that other types of state laws concerning aliens do not
necessarily fall within the preempted field of alien registration. In its 1976 decision in De Canas
v. Bica, for example, the Court held that federal law did not preempt a California law prohibiting

146 Id. at 236. The Rice Court also held that certain state law claims—for example, an allegation that the warehouse had
violated state law by failing to secure state approval for certain construction contracts—survived preemption because
they involved fields that the Warehouse Act did not address. Id. at 236-37.
147 See Arizona v. United States, 567 U.S. 387 (2012). Under the Immigration and Nationality Act, the term “alien”
refers to “any person not a citizen or national of the United States.” 8 U.S.C. § 1101(a)(3).
148 312 U.S. 52, 72–74 (1941).
149 Id. at 66–67. While Hines did not hold that federal power over alien regulation was “exclusive,” subsequent
Supreme Court cases have characterized it as a field preemption decision. See Arizona, 567 U.S. at 401.
150 Arizona, 567 U.S. at 401–02 (“Federal law makes a single sovereign responsible for maintaining a comprehensive
and unified system to keep track of aliens within the Nation’s borders.”).
151 8 U.S.C. § 1304(e).
152 Arizona, 567 U.S. at 400–03. Even though a violation of the identification card requirement was already punishable
as a misdemeanor under federal law, the Arizona statute made violation of the requirement a state misdemeanor. Id.
153 Id.
154 Id.
155 Id. at 401–03. In Arizona, the Court also invalidated two other provisions of the relevant Arizona law because they
conflicted with federal law. First, the Court held that federal law preempted an Arizona provision that prohibited
unauthorized aliens from seeking work. Id. at 406–07. Second, the Court held that federal law preempted a provision in
the Arizona statute that allowed state police to arrest without a warrant persons whom they had probable cause to
believe committed a removable offense. Id. at 410. The Court reasoned that this provision conflicted with federal
objectives by allowing state police to perform the functions of an immigration officer in circumstances not authorized
by federal law. Id. at 408–09.
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the employment of aliens not entitled to lawful residence in the United States.156 The Court based
this conclusion on the absence of provisions regulating employment eligibility in the INA at the
time.157
The Court has also upheld several state laws regulating the activities of aliens since De Canas. In
Chamber of Commerce v. Whiting, for example, the Court held that federal law did not preempt
an Arizona statute allowing the state to revoke an employer’s business license for hiring aliens
who did not possess work authorization.158
Nuclear Energy: Safety Regulation
The Supreme Court has also held that federal law preempts the field of nuclear safety regulation.
The Court has explained, however, that this field does not encompass all state laws that affect
safety decisions made by nuclear power plants. Instead, the Court has concluded that state laws
fall within the preempted field of nuclear safety regulation if they (1) are motivated by safety
concerns and implicate a “core federal power,” or (2) have a “direct and substantial” effect on
safety decisions made by nuclear facilities.159
This division of authority is the result of a regulatory regime that has changed significantly over
the course of the 20th century. The federal government initially maintained a monopoly over the
use, control, and ownership of nuclear technology.160 Beginning in 1954, however, the Atomic
Energy Act (AEA) allowed private entities to own, construct, and operate nuclear power plants
subject to a “strict” licensing and regulatory regime administered by the Atomic Energy
Commission (AEC).161
In 1959, Congress amended the AEA to give the states greater authority over nuclear energy
regulation. The 1959 Amendments allowed states to assume responsibility over certain nuclear
materials as long as their regulations were “coordinated and compatible” with federal
requirements.162 While the 1959 Amendments reserved certain key authorities to the federal
government, they also affirmed the states’ authority to regulate “activities for purposes other than
protection against radiation hazards.”163 Congress reorganized the administrative framework
surrounding these regulations in 1974, when it replaced the AEC with the Nuclear Regulatory
Commission (NRC).164
The Supreme Court has held that, although this regulatory scheme preempts the field of nuclear
safety regulation, certain state regulations of nuclear power plants that have a non-safety rationale
fall outside this preempted field.
The Court identified this distinction in Pacific Gas & Electric Co. v. State Energy Resources
Conservation & Development Commission, where it held that federal law did not preempt a

156 424 U.S. 351 (1976).
157 Id. at 359. De Canas pre-dated the current federal work authorization rules for aliens. See 8 U.S.C.
§ 1324a(a)(1)(A).
158 563 U.S. 582, 587 (2011). In Whiting, the Court also upheld a provision of the Arizona law that required employers
to use the “E-Verify” program, which allows users to verify a person’s work authorization status. See id. at 608–09.
159 See Va. Uranium, Inc. v. Warren, 139 S. Ct. 1894, 1904 (2019) (Gorsuch, J, lead opinion); English v. Gen. Elec.
Co., 496 U.S. 72, 84–85 (1990).
160 English, 496 U.S. at 80.
161 Id. at 81–82; 42 U.S.C. § 2011.
162 42 U.S.C. § 2021(g).
163 Id. § 2021(k).
164 Id. §§ 5814, 5841.
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California statute regulating the construction of new nuclear power plants.165 The California
statute conditioned the construction of new nuclear power plants on a state agency’s
determination concerning the availability of adequate storage facilities and means of disposal for
spent nuclear fuel.166 In challenging this statute, two public utilities contended that federal law
made the federal government the “sole regulator of all matters nuclear.”167
The Supreme Court rejected this argument, reasoning that the relevant statutes reflected
Congress’s intent to allow states to regulate nuclear power plants for non-safety purposes.168 The
Court then concluded that the California law was not preempted because it was motivated by
concerns over electricity generation and the economic viability of new nuclear power plants—not
a desire to intrude into the preempted field of nuclear safety regulation.169
In addition to holding that the AEA does not preempt all state statutes and regulations concerning
nuclear power plants, the Court has upheld the availability of certain state tort claims related to
injuries sustained by power plant employees.
In Silkwood v. Kerr-McGee Corp., the Court upheld a punitive damages award against a nuclear
laboratory arising from an employee’s injuries from plutonium contamination.170 The Court
rejected the laboratory’s argument that the damages award impermissibly punished and deterred
conduct related to the preempted field of nuclear safety.171 In rejecting this argument, the Court
observed that Congress had not provided alternative federal remedies for persons injured in
nuclear accidents.172 This omission was significant, the Court reasoned, because it was “difficult
to believe” that Congress would have removed all judicial recourse from plaintiffs injured in
nuclear accidents without an explicit statement to that effect.173
The Court also reasoned that Congress had assumed the continued availability of state tort
remedies when it adopted a 1957 amendment to the AEA.174 Under the relevant amendment, the
federal government partially indemnified power plants for certain liabilities for nuclear accidents.

165 461 U.S. 190, 216 (1983).
166 Id. at 194.
167 Id. at 205.
168 Id.
169 Id. at 213–16. In its 2019 decision in Virginia Uranium, Inc. v. Warren, the Court clarified that AEA preemption
will depend on this type of inquiry into the motivations of a challenged state law only when the state law implicates a
“core federal power” reserved to the NRC. 139 S. Ct. 1894, 1904 (2019) (Gorsuch, J., lead opinion); id. at 1909
(Ginsburg, J., concurring in the judgment). In that case, the Court held that federal law did not preempt a Virginia
statute banning the mining of uranium—a radioactive metal used in the production of nuclear fuel. See id. at 1900
(Gorsuch, J., lead opinion); id. at 1912 (Ginsburg, J., concurring in the judgment). Under the AEA and its subsequent
amendments, the NRC has the authority to regulate the milling, transfer, use, and disposal of uranium, but not uranium
mining conducted on private lands. See id. at 1900 (Gorsuch, J., lead opinion). In upholding the Virginia mining ban, a
majority of the Court declined to evaluate the state’s underlying motivation, explaining that such an inquiry is
appropriate (if at all) only when state law regulates an activity related to the NRC’s “core federal powers” under the
AEA. See id. at 1904 (Gorsuch, J., lead opinion); id. at 1912–14 (Ginsburg, J., concurring in the judgment). While the
Court interpreted Pacific Gas as recognizing that the construction of nuclear power plants involves one of these “core
federal powers,” a majority of the Justices agreed that uranium mining does not implicate similar federal authorities
because it falls outside the NRC’s jurisdiction. See id. at 1904 (Gorsuch, J, lead opinion); id. at 1912 (Ginsburg, J.,
concurring in the judgment). The Court accordingly relied on this distinction to uphold the Virginia law without
evaluating its underlying purpose.
170 464 U.S. 238, 241–42 (1984).
171 Id. at 249.
172 Id.
173 Id.
174 Id. at 251–52.
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According to the Court, this scheme reflected an assumption that plaintiffs injured in such
accidents retained the ability to bring tort claims against the power plants.175
The Supreme Court applied this reasoning from Silkwood six years later in English v. General
Electric Co., where it held that federal law did not preempt state tort claims alleging that a
nuclear laboratory had retaliated against a whistleblower for reporting safety concerns.176
In allowing the claims to proceed, the Court rejected the argument that federal law preempts all
state laws that affect plants’ nuclear safety decisions. Rather, the Court explained that a state law
must have a “direct and substantial” effect on such decisions in order to fall within the federally
preempted field of nuclear safety regulation.177 While the Court acknowledged that the relevant
tort claims may have had “some effect” on safety decisions by making retaliation against
whistleblowers more costly than safety improvements, it concluded that such an effect was not
sufficiently “direct and substantial” to render the claims preempted.178
In making this assessment, the Court relied on Silkwood, where it held that the relevant punitive
damages award fell outside the field of nuclear safety regulation despite its likely impact on
safety decisions.179 Because the Court concluded that the type of damages award at issue in
Silkwood affected safety decisions more directly and “far more substantially” than the
whistleblower’s retaliation claims, it held that the retaliation claims were not preempted.180
Takeaways
A determination that federal law preempts a field has powerful consequences, displacing even
state laws and regulations that are consistent with or complementary to federal law.181 Because of
these effects, the Supreme Court has cautioned against overly hasty inferences that Congress has
occupied a field.182 The Court has rejected the argument that the comprehensiveness of a federal
regulatory scheme is sufficient to conclude that federal law occupies a field, explaining that
Congress and federal agencies often adopt “intricate and complex” laws and regulations without
intending to assume exclusive regulatory authority over the relevant subjects.183

175 Id. at 250–52.
176 496 U.S. 72, 90 (1990).
177 Id. at 85.
178 Id.
179 Id. at 85–86.
180 Id. at 86.
181 See Arizona v. United States, 567 U.S. 387, 401–02 (2012); Rice v. Santa Fe Elevator Corp., 331 U.S. 218, 230
(1947).
182 See O’Melveny & Myers v. FDIC, 512 U.S. 79, 85 (1994) (“Nor would we adopt a court-made rule to supplement
federal statutory regulation that is comprehensive and detailed; matters left unaddressed in such a scheme are
presumably left subject to the disposition provided by state law.”); see also Southland Corp. v. Keating, 465 U.S. 1, 18
(1984) (Stevens, J., concurring in part and dissenting in part) (“[E]ven where a federal statute does displace State
authority, it rarely occupies a legal field completely, totally excluding all participation by the legal systems of the
states.”) (citation and internal quotation marks omitted).
183 See N.Y. State Dep’t of Social Servs. v. Dublino, 413 U.S. 405, 415 (1973). See also Hillsborough Cnty. v.
Automated Med. Lab’ys, Inc., 471 U.S. 707, 716–17 (1985) (explaining that courts should not infer field preemption
“whenever an agency deals with a problem comprehensively,” because such an inference would be inconsistent with
“the federal-state balance embodied in [the Court’s] Supremacy Clause jurisprudence”).
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The Court has sometimes relied on legislative history and statutory structure—in addition to the
comprehensiveness of federal regulations—in assessing field preemption arguments.184 It is
unclear, however, to what extent the Court might rely on even these sources in future cases.185
The Court has also adopted a narrow view of the scope of certain preempted fields. For example,
the Court has rejected the proposition that federal nuclear energy regulations preempt all state
laws that affect the preempted field of nuclear safety regulation. Rather, the Court has explained
that, when a core federal power is not at issue, state laws fall within that field only if they have a
“direct and substantial” effect on it.186
As a corollary to this principle, the Supreme Court has held that—in certain contexts—generally
applicable state laws are more likely to fall outside a federally preempted field than state laws that
“target” entities or issues within the field. In Oneok, Inc. v. Learjet, Inc., for example, the Court
held that state antitrust claims against natural gas pipelines fell outside the preempted field of
interstate natural gas wholesaling because the relevant state antitrust law was not “aimed” at
natural gas companies and instead applied broadly to all businesses.187
Finally, the Court’s case law underscores that Congress can narrow the scope of a preempted field
with explicit statutory language. In Pacific Gas, for example, the Court held that the preempted
field of nuclear safety regulation did not encompass state laws motivated by non-safety concerns
based in part on a statutory provision disavowing such an intent.188 While the Court has
subsequently narrowed the circumstances in which it will apply Pacific Gas’s purpose-centric
inquiry to state laws affecting nuclear energy,189 it has reaffirmed the general principle that
Congress can circumscribe a preempted field’s scope with non-preemption clauses.190
Conflict Preemption
Federal law also impliedly preempts conflicting state laws.191 The Supreme Court has identified
two subcategories of conflict preemption. First, federal law impliedly preempts state law when it
is impossible for regulated parties to comply with both sets of laws (impossibility preemption).192
Second, federal law impliedly preempts state laws that pose an obstacle to the “full purposes and
objectives” of Congress (obstacle preemption).193 The two subsections below discuss these
subcategories of conflict preemption.

184 See, e.g., Rice v. Santa Fe Elevator Corp., 331 U.S. 218, 232–36 (1947); De Canas v. Bica, 424 U.S. 351, 359–60
(1976).
185 See Bates v. Dow Agrosciences LLC, 544 U.S. 431, 459 (2005) (Thomas, J., concurring in part and dissenting in
part) (noting “this Court’s increasing reluctance to expand federal statutes beyond their terms through doctrines of
implied pre-emption”); Camps Newfound/Owatonna, Inc. v. Town of Harrison, 520 U.S. 564, 617 (1997) (Thomas, J.,
dissenting) (“[O]ur recent cases have frequently rejected field pre-emption in the absence of statutory language
expressly requiring it.”); Kurns v. R.R. Friction Prods. Corp., 565 U.S. 625, 640–41 (2012) (Sotomayor, J., concurring
in part and dissent in part) (quoting Justice Thomas’s language from Camps Newfound).
186 English v. Gen. Elec. Co., 496 U.S. 72, 85 (1990).
187 575 U.S. 373, 384–88 (2015); see also English, 496 U.S. at 83 (explaining in dicta that generally applicable criminal
laws are not likely to fall within the preempted field of nuclear safety regulation).
188 Pac. Gas & Elec. Co. v. State Energy Res. Conservation & Dev. Comm’n, 461 U.S. 190, 209–10, 213–14 (1983).
189 See supra note 169.
190 See Va. Uranium, Inc. v. Warren, 139 S. Ct. 1894, 1902–3 (2019) (Gorsuch, J., lead opinion); id. at 1912–13
(Ginsburg, J., concurring in the judgment).
191 See Gade v. Nat’l Solid Wastes Mgmt. Ass’n, 505 U.S. 88, 108 (1992).
192 Fla. Lime & Avocado Growers, Inc. v. Paul, 373 U.S. 132, 142–43 (1963).
193 Hines v. Davidowitz, 312 U.S. 52, 67 (1941).
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Impossibility Preemption
The Supreme Court has held that federal law preempts state law when it is impossible to comply
with both sets of laws.194 To illustrate this principle, the Court has explained that a hypothetical
federal law forbidding the sale of avocados with more than 7% oil content would preempt a state
law forbidding the sale of avocados with less than 8% oil content, because avocado sellers could
not sell their products and comply with both laws.195
The Court has characterized impossibility preemption as a “demanding defense,”196 and its case
law on the issue is not as well developed as other areas of its preemption jurisprudence.197 Even
so, the Court has addressed impossibility preemption in two decisions concerning prescription
drug labeling.
Generic Drug Labeling
In PLIVA, Inc. v. Mensing and Mutual Pharmaceutical Co. v. Bartlett, the Supreme Court held
that federal regulations of generic drug labels preempted certain state law claims brought against
generic drug manufacturers because it was impossible for the manufacturers to comply with both
federal and state law.198
In both cases, plaintiffs alleged that they suffered adverse effects from certain generic drugs and
argued that the drugs’ labels should have included additional warnings.199 In response, the drug
manufacturers argued that the Hatch-Waxman Amendments (Hatch-Waxman) to the Food, Drug,
and Cosmetic Act preempted the state law claims.200
Under Hatch-Waxman, drug manufacturers can secure Food and Drug Administration (FDA)
approval for generic drugs by demonstrating that they are equivalent to a brand-name drug
already approved by the FDA.201 In doing so, the generic drug manufacturers need not comply
with the FDA’s standard preapproval process, which requires extensive clinical testing and the
development of FDA-approved labeling.202 They must, however, ensure that the labels for their
drugs are the same as the labels for corresponding brand-name drugs, meaning that generic
manufacturers cannot unilaterally change their labels.203
In both PLIVA and Bartlett, the Court held that the Hatch-Waxman Amendments preempted the
relevant state law claims because it was impossible for the generic drug manufacturers to comply
with both federal and state law.204 The Court reached this conclusion because federal law

194 Fla. Lime, 373 U.S. at 142–43.
195 Id.
196 Wyeth v. Levine, 555 U.S. 555, 573 (2009).
197 See Meltzer, supra note 41, at 8 (describing situations in which it is impossible to comply with both state and federal
requirements as “rare”).
198 564 U.S. 604, 618 (2011); 570 U.S. 472, 493 (2013).
199 PLIVA, 564 U.S. at 610; Bartlett, 570 U.S. at 475.
200 PLIVA, 564 U.S. at 610; Bartlett, 570 U.S. at 475.
201 See PLIVA, 564 U.S. at 612.
202 Id. at 612–13; Bartlett, 570 U.S. at 476–77.
203 PLIVA, 564 U.S. at 612–13; Bartlett, 570 U.S. at 477. For further information on the approval and labeling process
for generic drugs under Hatch-Waxman and related laws, see CRS Report R46778, The Generic Drug User Fee
Amendments (GDUFA): Background and Reauthorization, by Agata Bodie.
204 PLIVA, 564 U.S. at 617–18; Bartlett, 570 U.S. at 486–87.
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prohibited generic manufacturers from unilaterally altering their labels, while the state law claims
depended on the existence of a duty to make such alterations.205
In reaching this conclusion in PLIVA, the Court rejected the argument that it was possible for
manufacturers to comply with both federal and state law by petitioning the FDA to impose new
labeling requirements on the corresponding brand-name drugs.206 The Court rejected this
argument on the grounds that impossibility preemption occurs whenever a party cannot
independently comply with both federal and state law without seeking “special permission and
assistance” from the federal government.207
Similarly, in Bartlett, the Court rejected the argument that it was possible for generic drug makers
to comply with both federal and state law by refraining from selling the relevant drugs. The Court
rejected this “stop-selling” argument on the grounds that it would render impossibility preemption
“all but meaningless.”208 As a result, an evaluation of whether it is possible to comply with both
federal and state law must presuppose some affirmative conduct by the regulated party.
Despite its decisions in PLIVA and Bartlett, the Supreme Court has rejected impossibility
preemption arguments made by brand-name drug manufacturers, who are entitled to unilaterally
strengthen the warning labels for their drugs. In Wyeth v. Levine, the Court held that federal law
did not preempt a state law failure-to-warn claim brought against a branded drug manufacturer,
reasoning that it was possible for the manufacturer to strengthen its label for the drug without
FDA approval.209
Obstacle Preemption
Federal law also impliedly preempts state laws that pose an “obstacle” to the “full purposes and
objectives” of Congress.210 In its obstacle preemption cases, the Supreme Court has held that state
law can interfere with federal goals by frustrating Congress’s intent to adopt a uniform system of
federal regulation; conflicting with Congress’s goal of establishing a regulatory “ceiling” for
certain products or activities; or by impeding the vindication of a federal right.211
The Court has also cautioned, however, that obstacle preemption does not justify a “freewheeling
judicial inquiry” into whether state laws are “in tension” with federal objectives, as such a
standard would undermine the principle that “it is Congress rather than the courts that preempts
state law.”212

205 PLIVA, 564 U.S. at 617–18; Bartlett, 570 U.S. at 486–87.
206 PLIVA, 564 U.S. at 616.
207 Id. at 623–24.
208 Bartlett, 570 U.S. at 488–89.
209 555 U.S. 555, 573 (2009). The Wyeth Court indicated, however, that an impossibility preemption defense may be
available to brand-name drug manufacturers when there is “clear evidence” that the FDA would have rejected a
proposed change to a brand-name drug’s label. Id. at 571. The Court further clarified this standard in its 2019 decision
in Merck Sharp & Dohme Corp. v. Albrecht, explaining that “clear evidence” requires drug manufacturers to
demonstrate that they “fully informed” the FDA of the justifications for the warning required by the relevant state law
and that the FDA nevertheless rejected the proposed change. 139 S. Ct. 1668, 1672 (2019).
210 See Hines v. Davidowitz, 312 U.S. 52, 67 (1941).
211 See id.; Geier v. American Honda Motor Co., Inc., 529 U.S. 861, 875 (2000); Felder v. Casey, 487 U.S. 131, 153
(1988).
212 Chamber of Commerce v. Whiting, 563 U.S. 582, 607 (2011) (quoting Gade v. Nat’l Solid Wastes Mgmt. Ass’n,
505 U.S. 88, 111 (1992) (Kennedy, J., concurring in part and concurring in judgment)).
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The subsections below discuss a number of cases in which the Court has held that state law poses
an obstacle to the accomplishment of federal goals.
Foreign Sanctions
The Supreme Court has concluded that state laws can pose an obstacle to the accomplishment of
federal objectives by interfering with Congress’s choice to concentrate decisionmaking in federal
authorities.
The Court’s decision in Crosby v. National Foreign Trade Council illustrates this type of conflict
between state law and federal policy goals.213 In Crosby, the Court held that a federal statute
imposing sanctions on Burma preempted a Massachusetts statute that restricted state agencies’
ability to purchase goods or services from companies doing business with Burma.214
The Court identified several ways in which the Massachusetts law interfered with the federal
statute’s objectives. First, the Court reasoned that the Massachusetts law interfered with
Congress’s decision to provide the President with the flexibility to add or waive sanctions in
response to ongoing developments.215
Second, the Court explained that, by penalizing certain individuals and conduct that Congress
explicitly excluded from federal sanctions, the Massachusetts statute interfered with the federal
statute’s goal of limiting the economic pressure imposed by the sanctions to “a specific range.”216
In identifying this conflict, the Court rejected the state’s argument that its law shared the same
goals as the federal statute. Instead, the Court reasoned that the additional sanctions imposed by
the state law would undermine Congress’s intended “calibration of force.”217
Third, the Court concluded that the Massachusetts law undermined the President’s capacity for
effective diplomacy by compromising his ability “to speak for the Nation with one voice.”218
Automobile Safety Regulations
The Supreme Court has concluded that some federal laws and regulations evince an intent to
establish both a regulatory floor and ceiling for certain products and activities. The Court has
interpreted certain federal automobile safety regulations, for example, as not only imposing
minimum safety standards on carmakers, but as insulating manufacturers from certain forms of
stricter state regulation as well.
In Geier v. American Honda Motor Co., the Court held that the National Traffic and Motor
Vehicle Safety Act (NTMVSA) and associated regulations impliedly preempted state tort claims
alleging that an automobile manufacturer had negligently designed a car without a driver’s side
airbag.219 While the Court rejected the argument that the NTMVSA expressly preempted the state

213 530 U.S. 363, 366–67 (2000).
214 Id. at 366–67, 373–74. As the Court noted in Crosby, Burma changed its name to Myanmar in 1989. See id. at 366
n.1. However, because the parties in Crosby referred to the country as Burma, the Court followed suit. Id.
215 Id. at 376.
216 Id. at 377–79.
217 Id. at 379–80. After Crosby, Congress has included specific language in certain sanctions statutes that explicitly
allows states to pass sanctions laws of their own. See, e.g., Comprehensive Iran Sanctions, Accountability, and
Divestment Act of 2010, P.L. 111-195, § 202, 124 Stat. 1312, 1342–43.
218 Crosby, 530 U.S. at 380–81.
219 529 U.S. 861, 865 (2000).
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law claims,220 it reasoned that the claims interfered with the federal objective of giving car
manufacturers the option of installing a “variety and mix” of passive restraints.221
The Court discerned this goal from, among other things, the history of the relevant regulations
and Department of Transportation (DOT) comments indicating that the regulations were intended
to lower costs, incentivize technological development, and encourage gradual consumer
acceptance of airbags, rather than impose an immediate requirement.222 The Court thus held that
the NTMVSA impliedly preempted the state law claims because they conflicted with these
federal goals.223
The Court has rejected, however, the argument that federal automobile safety standards impliedly
preempt all state tort claims concerning automobile safety. In Williamson v. Mazda Motor of
America, Inc., the Court held that a different federal safety standard did not preempt a state law
claim alleging that a carmaker should have installed a certain type of seatbelt in a car’s rear
seat.224
While the regulation at issue in Williamson allowed manufacturers to choose between two
seatbelt options, the Court distinguished the case from Geier on the grounds that the DOT’s
decision to offer carmakers a choice was not a “significant” regulatory objective.225 Specifically,
the Court reasoned that the state tort action did not conflict with the purpose of the relevant
federal regulation, because the DOT’s decision to offer manufacturers an option was based on
relatively minor design and cost-effectiveness concerns.226
Federal Civil Rights
The Supreme Court has also held that state law can pose an obstacle to federal goals where it
impedes the vindication of federal rights.
In Felder v. Casey, the Court held that 42 U.S.C. § 1983 (Section 1983)—which provides
individuals with the right to sue state officials for federal civil rights violations—preempted a
state statute adopting certain procedural rules for bringing Section 1983 claims in state court.227
The state statute required Section 1983 plaintiffs to provide government defendants 120 days’
written notice of the circumstances giving rise to their claims, the amount of their claims, and
their intent to bring suit.228
The Court held that federal law preempted these requirements because their purpose and effect
conflicted with Section 1983’s remedial objectives.229 Specifically, the Court reasoned that the
requirements’ purpose of minimizing the state’s liability conflicted with Section 1983’s goal of
providing relief to individuals whose constitutional rights are violated by state officials.230 The
Court also concluded that the state statute’s effects interfered with federal objectives because the

220 See supra “Compliance Savings Clauses.”
221 Geier, 529 U.S. at 881.
222 Id. at 874–75.
223 Id. at 881.
224 562 U.S. 323 (2011).
225 Id. at 332.
226 Id. at 335.
227 487 U.S. 131, 153 (1988).
228 Id. at 134.
229 Id. at 138.
230 Id. at 141–42.
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statute’s enforcement would result in different outcomes in Section 1983 litigation based on
whether a claim was brought in state or federal court.231
Takeaways
The Supreme Court has held that state law can conflict with federal law in a number of ways.
State law can conflict with federal law when it is impossible to comply with both sets of laws.
While the Court has characterized this type of impossibility preemption argument as a
“demanding defense,”232 its decisions in PLIVA and Bartlett arguably extended the doctrine’s
scope.233 In those cases, the Court made clear that impossibility preemption remains a viable
defense even in instances in which a regulated party can petition the federal government for
permission to comply with state law234 or stop selling a regulated product altogether.235
State law can also conflict with federal law when it poses an obstacle to federal goals. In
evaluating congressional intent in obstacle preemption cases, the Court has relied upon statutory
text,236 structure,237 and legislative history238 to determine a statute’s preemptive scope.
Relying on these indicia of legislative purpose, the Court has held that state laws can pose an
obstacle to federal goals by interfering with a uniform system of federal regulation,239 imposing
stricter requirements than federal law (where federal law evinces an intent to establish a
regulatory ceiling),240 or by impeding the vindication of a federal right.241
While obstacle preemption has played an important role in the Court’s preemption jurisprudence
since the mid-20th century, recent developments have called the scope of the doctrine into
question. Commentators have noted the tension between increasingly popular textualist theories
of statutory interpretation (which generally reject extratextual evidence as a possible source of
statutory meaning) and obstacle preemption doctrine (which potentially requires courts to consult
such evidence).242
Identifying this possible inconsistency, Justice Thomas has categorically rejected the Court’s
obstacle preemption jurisprudence, criticizing the Court for “routinely invalidat[ing] state laws
based on perceived conflicts with broad federal policy objectives, legislative history, or
generalized notions of congressional purposes that are not embodied within the text of federal
law.”243

231 Id. at 138.
232 Wyeth v. Levine, 555 U.S. 555, 573 (2009).
233 See Ernest A. Young, “The Ordinary Diet of the Law”: The Presumption Against Preemption in the Roberts Court,
2011 SUP. CT. REV. 253, 327–28 (2011) (characterizing PLIVA as an “expansion” of impossibility preemption).
234 PLIVA, Inc. v. Mensing, 564 U.S. 604, 623–24 (2011).
235 Mutual Pharm. Co. v. Bartlett, 570 U.S. 472, 488 (2013).
236 See Crosby v. Nat’l Foreign Trade Council, 530 U.S. 363, 380 (2000).
237 See id. at 377–80.
238 See id. at 375 n.9.
239 Id. at 374–77.
240 Geier, 529 U.S. at 875.
241 Felder v. Casey, 487 U.S. 131, 153 (1988).
242 Note, Preemption as Purposivism’s Last Refuge, 126 HARV. L. REV. 1056, 1065 (2013). See also Meltzer, supra
note 41, at 35–43 (considering whether obstacle preemption is consistent with textualism).
243 Wyeth v. Levine, 555 U.S. 555, 583 (2009) (Thomas, J., concurring in the judgment).
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Federal Preemption: A Legal Primer

Justice Thomas’s skepticism toward obstacle preemption arguments has drawn additional support
in recent cases, especially from Justice Gorsuch. In the Court’s decision in Virginia Uranium, Inc.
v. Warren, Justice Gorsuch authored an opinion joined by Justices Thomas and Kavanaugh in
which he rejected the proposition that implied preemption analysis should appeal to “abstract and
unenacted legislative desires” not reflected in a statute’s text.244
While Justice Gorsuch did not there explicitly endorse a wholesale repudiation of obstacle
preemption, he later joined Justice Thomas’s call for the Court to abandon its “purposes and
objectives” preemption jurisprudence in a 2020 concurring opinion.245 Although skepticism
toward obstacle preemption arguments has drawn additional support in recent Supreme Court
cases, to date it has remained a minority view.

Author Information

Bryan L. Adkins
Jay B. Sykes
Legislative Attorney
Legislative Attorney

Alexander H. Pepper

Legislative Attorney

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244 Va. Uranium, Inc. v. Warren, 139 S. Ct. 1894, 1907 (2019).
245 Kansas v. Garcia, 140 S. Ct. 791, 807 (2020) (Thomas, J., concurring). Justice Gorsuch also joined Justice Thomas’s
concurrence with the denial of certiorari in Lipschultz v. Charter Advanced Servs. (MN), LLC, 140 S. Ct. 6 (2019), in
which Justice Thomas expressed doubt that a federal agency policy can serve as the basis for preemption of state law.
Id. at 7.
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