Law of Pre- emption: a Critical Evaluation


Preemption is the rule of law that if the federal government through Congress has enacted legislation on a subject matter it shall be controlling over state laws and/or preclude the state from enacting laws on the same subject if Congress has specifically declared it has “occupied the field.”  Preemption can occur by Congress passing a law, preempting state or local law. It is “well established”‘[1] that Congress has the power to preempt state law in a given area.   If Congress has not clearly claimed preemption, a federal or state court may examine legislative history to determine the lawmakers’ intent toward preemption. The only issue in preemption cases is whether Congress has in fact exercised this undoubted power. Such exercise is a matter of the intent of Congress, and the issue is resolved by an analysis of that intent. The apparent precision, orderliness, and axiomatic quality of this black-letter position, however, conceal fundamental confusion in the thinking of judges and scholars alike about the underlying nature of preemption. Although as a topic, preemption has largely been ignored by constitutional law scholars, it is almost certainly the most frequently used doctrine of constitutional law in practice.[2] This fact alone should ensure the importance of exposing and resolving the profound confusion at the heart of preemption law, which is belied by the seemingly simple statement of its provisions. But there is another reason for the importance of this task. This is the centrality of the issue of the internal division of political power within the growing fields of comparative constitutional law in general, and comparative federalism in particular. The granting of a power of preemption to the central government is a common, but not a necessary, feature of a federal state. Thus, preemption is a critical legal concept that helps to define the nature of any federal political system.

Statements of preemption law almost routinely “start from the top” with a reference to the Supremacy Clause, although the exact connection that is claimed to exist between the two often varies. In fact, in order of descending frequency and significance, three different theories regarding the nature of the connection can be reconstructed from the literature. First, Congress’s constitutional power to preempt state law derives from the Supremacy Clause.  Second, regardless of the source of the preemption power; the Supremacy Clause operates to preempt state law where it conflicts with federal law.[3] Third, each case of preemption involves a conflict between Congress’s intent to displace state regulation in a given area, and the intent of the state or states to regulate that same area. According to this view, the Supremacy Clause operates to resolve this conflict in favor of Congress.[4]

Part I argues that preemption and supremacy are quite distinct legal and constitutional concepts. Part II demonstrates that each of the three asserted connections is the result of muddled thinking about preemption and supremacy, and establishes that the two have little to do with each other. Part III turns from conceptual to historical analysis of the difference between supremacy and preemption. Part IV discusses the implications of the previous analysis.


Supremacy and preemption are quite distinct legal concepts and constitute two alternative methods of regulating the relationship between concurrent federal and state powers. The supremacy of federal law means that valid federal law overrides otherwise valid state law in cases of conflict between the two. In itself, federal supremacy does not deprive states of their preexisting, concurrent lawmaking powers in a given area; rather, it means that a particular state law in conflict with a particular federal law will be trumped in cases where both apply. Preemption, by contrast, means (a) that states are deprived of their power to act at all in a given area, and (b) that this is so whether or not state law is in conflict with federal law.[5] When states lose their concurrent lawmaking powers through preemption by Congress, the issue of potential substantive conflict between the content of valid state and federal laws is simply not reached, for the state no longer has power to legislate at all in the given area.

It is first necessary to define the question properly. Whether federal law displaces state law depends on the division of federal and state legislative authority. Within this inquiry, the constitutional structure is straightforward: Article I, Section 8 enumerates the powers of Congress; Article I, Section 9 limits the powers of Congress; Article I, Section 10 limits the powers of the states; and the Tenth Amendment reserves to the states the legislative powers not delegated to Congress and prohibited to the states. Importantly, Clause 2 of Article VI, the Supremacy Clause, provides that congressional enactments consistent with the Constitution “shall be the supreme Law of the Land. Although this provision in effect gives to Congress “an extraordinary power in a federalist system, it is critically important to note the Supremacy Clause itself does not authorize Congress to preempt state laws.

The Supremacy Clause is relevant only at the post-enactment stage, where a state law conflicts to some degree with a federal law; the clause specifies that the federal law would trump the state law in that event.[6]The power to preempt state law, if one exists, must be found elsewhere in the Constitution, most logically in the affirmative grants of power to Congress under Article I, Section 8. Therefore, should Congress legislate pursuant to its power, say, to regulate interstate commerce and further include a provision expressly preempting certain state laws, the authority for the preemption provision must come from either the Commerce Clause alone or perhaps the Commerce Clause with a helping hand from the Necessary and Proper Clause. Preemption is not a substantive power of Congress, but rather a method of regulation in furtherance of some other substantive congressional authority.


Given this constitutional structure, to the extent there are questions of constitutional policy in preemption-questions about the relative power of Congress and of the state legislatures, “the Danger . . . that the national would swallow up the State Legislatures,[7] and the like-those questions were answered by the framers with the specific enumerations and limitations of federal legislative power in Article I and the inclusion of the Supremacy Clause in the Constitution. When Congress has legislated consistent with its limited, enumerated powers, the question ceases to be one about the vertical distribution of powers between federal and state governments-after all, the Constitution gave Congress the power to legislate, and Congress has exercised that power. Rather, the question becomes one of the horizontal divisions of federal governmental functions among the three branches. Thus, preemption analysis starts 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.[8] In the proper context, this assumption is perfectly legitimate, and the intuition behind it is certainly understandable.

Federal law is generally interstitial in nature. It rarely occupies a legal field completely, totally excluding all participation by the legal systems of the states…. Federal legislation, on the whole, has been conceived and drafted on an ad hoc basis to accomplish limited objectives. It builds upon legal relationships established by the states, altering or supplanting them only in so far as necessary for the special purpose. Congress acts, in short, against the background of the total corpus juries of the states in much the way that a state legislature acts against the background of the common law, assumed to govern unless changed by legislation.[9]


Both express and conflict preemption involve an actual conflict between the state law and some federal statutory language, either the preemption provision or a primary provision. Implied preemption doctrines displace state law absent any actual conflict with some federal provision, and consequently, things start getting a bit murkier.

The operation of obstacle preemption significantly differs from express or conflict preemption because there is no direct conflict with any federal law precisely on point-for example, either the preemption provision or a primary regulatory provision. Obstacle preemption thus moves the displacement analysis along the spectrum away from the direct action extreme by both relaxing the standard for conflict-from direct conflict to obstacle to accomplishment-and expanding the evidence of congressional intent-from statutory text to purposes and objectives. Such progression challenges the notion of a generalized presumption against preemption because both doctrinal alterations infuse more ambiguity into the analysis.[10] Yet; it is in this area of implied preemption that the Court most often invokes the presumption against preemption.


Field preemption displaces state law even where it may not frustrate any purpose of Congress or conflict in any way with some federal statutory provision. Interstitial state laws complementary to the federal scheme are displaced where Congress has-implicitly-marked the regulatory area as its own-in other words, has occupied the field. The Court will infer such intent to strip state legislative jurisdiction where Congress legislates: (1) in a manner “so pervasive as to make reasonable the inference that Congress left no room for the States to supplement it, or (2) in “a field in which the federal interest is so dominant that the federal system (must) be assumed to preclude the enforcement of state laws on the same subject.[11]

With respect to the first strand, it may seem odd at first blush that an analysis of the structural division of powers between two parties-here, federal and state legislatures-is dependent upon the aggrandizing actions of one of the two parties-Congress’s pervasive legislation-and thus returns us to the initial query whether preemption jurisprudence should depend at all on the prevailing winds of legislative activity. Logic is stretched further if one grafts onto the structural analysis a general presumption against preemption-favoring the nonnative entity, the state. After all, a field preemption case, Rice v. Santa Fe Elevator Corp., gave life to our sacred cow-the oft-quoted “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.[12] Even if the clear and manifest purpose requirement can be said to have been met simply by the comprehensiveness and pervasiveness of federal regulation, a presumption against preemption at least would permit the States to regulate interstitially rather than be displaced altogether.


From this point it is only a small step to displacement of state law by federal common law. The review thus far summarizes the various strands of preemption analysis, but it does not complete the picture of federal displacement of state law. Preemption displaces state laws that stand in conflict, however tangentially, with some congressional enactment.[13] However, state law can be displaced even without any legislative action whatsoever.

Thus, as in field preemption, a uniquely federal interest can substitute for legislative action to form the predicate federal law necessary to displace state law. But, unlike field preemption, the mere existence of strong federal interests does not suffice to displace state law.

Two relevant observations flow from Boyle. First, the analysis followed by the Court closely tracks the standard preemption and Supremacy Clause analysis offered above to explain the points on the spectrum leading up to the present context. The federal common-law rule operated to displace even an exercise of state power in an area of traditional state regulation-the protection of the health and safety of its citizens through tort law.


The theory behind the doctrine is rather elusive. The original conception posited that Congress enjoyed exclusive jurisdiction over matters that “are in their nature national, or admit of one uniform system.[14] The problem with this conception is that the language of the Commerce Clause (and of Article I, Section 8 generally) does not suggest exclusivity.

There are several ways to carry the burden. The simplest way is by reference to express statutory language-either a substantive regulation or a preemption provision-with which the state law conflicts; the Supremacy Clause resolves such conflicts in favor of the federal law[15]. The burden can also be carried, absent an express provision on point, by showing a state law conflict with more general characteristics of congressional activity in the same or related areas, such as the policy and objectives of Congress in obstacle preemption or the pervasiveness and comprehensiveness of the federal regulatory scheme in one strand of field preemption.  There is no conceivable reason why congressional inaction under the Commerce Clause should be deemed to have the same pre-emptive effect elsewhere accorded only to congressional action. There, as elsewhere, ‘Congress’ silence is just that-silence.[16]

Federal displacement of state law cannot be divided into discrete, Euclidean doctrinal boxes, but instead fits onto a rather smooth continuum. Progression on this continuous spectrum involves a substitution of directness or pervasiveness of congressional action for a strong or uniquely federal interest as the showing necessary to displace state law. On this spectrum, a presumption against preemption has no place other than as recognition, in specific contexts, of the background against which Congress legislates and thus against which courts interpret the meaning of such legislation.


Preemption is a critical legal concept that helps to define the nature of any federal political system. Once it is known which powers of the federal and state governments are exclusive and which concurrent, it is still necessary to determine whether the concurrent powers are subject only to the principle of supremacy or also to the power of preemption in order to understand the true division of powers in that federal system.

This assignment sought to make sense of extant mechanisms whereby federal law displaces state law and argued that there is not much logic to a general presumption against preemption in this doctrinal framework. Because the point is to synthesize and rationalize, the argument makes no normative judgments concerning the propriety of the various displacement doctrines.[17] Nevertheless, the analysis offered here may well seem heretical to “Our Federalism[18] and the principles that preserve and protect that delicate structure against the aggrandizing propensities of the national government. Many well-meaning and capable scholars have lamented the fact that expansive congressional power under Article I, Section 8, coupled with the displacing effect of preemption means that “the Danger … that the national will swallow up the State Legislatures[19] has been realized in the modem regulatory state. The solution, it is advocated, comes in the form of a strong presumption against preemption or a clear-statement rule in order to counterbalance the awesome preemptive effect of the Supremacy Clause. This solution seems to me to graft confusion on error. Properly applying the Supremacy Clause improves doctrinal coherence and permits the proper protection of uniquely federal interests.

So fundamentally redefining the balance of legislative powers between Congress and the states, of course, requires a coherent theory of the limits of Congress’s enumerated powers under Article I, Section 8. And such a theory would in turn call for a comprehensive assessment of legislative federalism– the division of powers between the federal and state legislatures and the mechanisms for maintaining such division. These broader questions are beyond the scope of this article. Suffice it to say here that attempting to patch jurisprudential cracks, caused by the want of such a solid theoretical foundation for legislative federalism, with preemption analysis is not only ineffective but may also be counterproductive. Returning preemption analysis to its proper place would provide doctrinal coherence, and at the same time free up intellectual and jurisprudential resources to design and construct the foundation essential for a proper balance of state and federal legislative authority.


Dinh, Viet D “Reassessing the law of preemption“. Georgetown Law Journal. 07 Nov, 2010.

See generally Alden v. Maine, 527 U.S. 706 (1999); College Sav. Bank v. Florida Prepaid Postsecondary Educ. Expense Bd., 527 U.S. 666 (1998); Printz v. United States, 521 U.S. 898 (1997); Seminole Tribe of Fla. v. Florida, 517 U.S. 44 (1996); United States v. Lopez, 514 U.S. 549 (1995); New York v. United States, 505 U.S. 144 (1992).

See Bratton; supra note 16, at 624-39 (tracing the historic oscillation of preemption doctrine between favoring federal interests and preserving state autonomy). 41. Dellmuth v. Muth, 491 U.S. 223, 230 (1989) (quoting Atascadero State Hosp. v. Scanlon, 473 U.S. 234, 242 (1985)).

See Catherine L. Fisk, The Last Article About the Language of ERISA Preemption? A Case Study on the Failure of Textualism, 33 HARv. J. oN LEGIS. 35, 44 n.38 (1996) (“If Gregory’s `plain statement’ rule were applied to preemption … entire bodies of preemption doctrine might be called into question.”),

See Debartolo v. Florida Gulf Coast Bldg. & Const. Trades Council, 485 U.S. 568, 575 (1988); Ashwander v. Tennessee Valley Auth., 297 U.S. 288, 329-30 (1936); Adrian Vermeule, Saving Constructions, 85 GEO. L.J. 1945 (1997).

See id. at 144 (holding that Congress may not compel a state to enact laws to further a federal radioactive waste regulatory program). 60. See Printz v. United States, 521 U.S. 898, 935 (1997) (invalidating federal regulation that state law enforcement officers perform background checks).

Cf. Silkwood v. Kerr-McGee Corp., 464 U.S. 238, 256 (1984) (stating that in the Atomic Energy Act, “Congress intended to stand by both concepts and to tolerate whatever tension there was between them”).

See Timothy Wilton, Federalism Issues in “No Airbag” Tort Claims: Preemption and Reciprocal Comity, 61 NoTRE DAME L. REv. 1, 27 (1986). 152. The two articles are also linked to each other by the reference in the middle of the provision to “any safety standard applicable to the same aspect of performance.” Id. (emphasis added).

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[1] Pacific Gas & Elec. Co. v. State Energy Comm’n, 461 U.S. 190, 203 (1983)

[2] A quick search on LEXIS revealed that the word “preemption” was mentioned in 49 Supreme Court cases in the last five terms alone.

[3] The exposition of preemption doctrine in virtually every modem preemption case includes a statement to this effect. See, e.g., Cipollone, 112 S.Ct. at 2617 (“[S]tate law is preempted if that law actually conflicts with federal law”) (citations omitted).

[4] -See infra notes 24-28 and accompanying text; See also infra part II.C.

[5] For a recent statement of the difference between supremacy and preemption in the context of the federal structure of the European Union, see Joseph H.H. Weiler, The Transformation of Europe, 100 YALE LJ. 2403, 2417 (1991).

[6] 34. What degree of conflict suffices-including whether any federal legislation is needed at all-and how much state law is displaced are answered by the various strands of preemption analysis, to which I return below at infra Part II.

[7] Farrand, supra note 22, at 160

[8] Rice v.  Santa Fe Elevator Corp., 331 U.S .  218, 230 (1947).


[10] . Cf. Florida Lime & Avocado Growers, Inc. v. Paul, 373 U.S. 132, 146-47 (1963) (noting the Court’s reluctance to displace state law “in the absence of an unambiguous congressional mandate to that effect”).

[11] Id. at 504 (quoting Rice, 331 U.S. at 230). 108. 331 U.S. 218 (1947).

[12] Id. at 230 (holding federal interest in establishing “fair and uniform business practices” supersedes state interest in regulating warehouse operations).

[13] See M’Culloch v. Maryland, 17 U.S. (4 Wheat.) 316, 436 (1819) (stating that “states have no power… to retard, impede, burden or in any other manner control the operation of the constitutional laws enacted by congress”)

[14] Cooley v. Board of Port Wardens, 53 U.S. (12 How.) 299, 319 (1851)

[15] See Wilkerson v. Rahrer, 140 U.S. 545, 561 (1891) (upholding a federal law permitting local

[16] See Noel T. Dowling, Interstate Commerce and State Power, 27 VA. L. REV. 1, 2-19 (1940).

[17] See, e.g., Nelson, supra note 20 (arguing that constitutional history and jurisprudence do not support obstacle preemption).

[18] Younger v. Harris, 401 U.S. 37, 44 (1971).

[19] Farrand, supra note 22, at 160 (statement of George Mason, June 7, 1787).