Tenth Amendment

Original public meaning

The clause restates a reserved-powers principle already familiar from the Articles of Confederation, but deliberately narrows its wording. Article II of the Confederation reserved to each state "every Power, Jurisdiction and right, which is not by this confederation expressly delegated to the United States." The word "expressly" does not appear in the Tenth Amendment, and its absence was a contested, recorded choice, not an oversight.

Madison's own pre-Convention use of the formula, 19 Feb. 1787

Every source on this page tracing the "expressly delegated" formula — Wilson, the Federal Farmer, Iredell, the 1789 congressional debate itself — dates from the ratification era or later. Elliot's Debates (Vol. V) preserves an earlier occurrence, in Madison's own diary of the Confederation Congress, three months before the Convention that would eventually strike the word. Arguing against Charles Pinckney's motion to stop federal troop enlistments raised to support Massachusetts against Shays' Rebellion, Madison invoked the Confederation's existing reserved-powers limit as a live doubt about Congress's own authority to intervene at all:

"He admitted, indeed, that it appeared rather difficult to reconcile an interference of Congress in the internal controversies of a state with the tenor of the Confederation, which does not authorize it expressly, and leaves to the states all powers not expressly delegated, or with the principles of republican governments, which, as they rest on the sense of the majority, necessarily suppose power and right always to be on the same side." — James Madison, Congress of the Confederation, 19 Feb. 1787

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This is the wiki's earliest instance of Madison himself using the "expressly delegated" formula — not as a proposed textual amendment to a not-yet-written Constitution, but as an existing Confederation-era limit he treats as a live obstacle to Congress's own preferred policy. Read against his 18 Aug. 1789 floor objection to Tucker's motion to insert "expressly" into the Tenth Amendment (below) — that it "was impossible to confine a Government to the exercise of express powers" — the two statements are not strictly inconsistent: in 1787 Madison invokes the word as a reason Congress should hesitate before acting; in 1789 he argues the word should not appear in the new Constitution's own text at all. The wiki holds both without resolving whether Madison's view changed or whether he always treated "expressly" as a rhetorical weight rather than a rule he wanted formally enacted.

On 18 Aug. 1789 the House considered the reserved-powers proposition. Mr. Tucker moved to insert "expressly" before "delegated." Madison objected that "it was impossible to confine a Government to the exercise of express powers; there must necessarily be admitted powers by implication, unless the Constitution descended to recount every minutia," and recalled that the same word had been proposed and abandoned in the Virginia ratifying convention. Sherman agreed, observing "that corporate bodies are supposed to possess all powers incident to a corporate capacity, without being absolutely expressed." On 21 Aug. 1789 Gerry's renewed motion to insert "expressly" was defeated 17–32 on a recorded vote. Sherman then supplied the final wording — "the powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people" — adopted without further debate.

James Wilson defended the underlying enumerated-powers design at the Pennsylvania ratifying convention (4 Dec. 1787), arguing the "line ... drawn between the powers of the general government and those of the particular state governments" was "as minutely enumerated and defined as was possible." The Federal Farmer, no. 16 (20 Jan. 1788), reasoned toward the same text the First Congress would later adopt, proposing that the Constitution "enumerate the powers given, and then in general words, according to the mode adopted in the 2d art. of the confederation, declare all powers, rights and privileges, are reserved, which are not explicitly and expressly given up." Madison's *Federalist* No. 45 (26 Jan. 1788) states the resulting allocation in its most quoted form:

"The powers delegated by the proposed Constitution to the Federal Government, are few and defined. Those which are to remain in the State Governments are numerous and indefinite." — James Madison, Federalist, no. 45, 26 Jan. 1788

James Iredell's proposed amendment at the North Carolina ratifying convention (1 Aug. 1788) anticipated the final text almost exactly, reserving to each state "every power, jurisdiction, and right, which is not by this Constitution delegated" and treating the Constitution as "a solemn instrument, defining the extent of their authority, and the limits of which they cannot rightfully in any instance exceed." See also Federalist No. 45 for Madison's fuller argument that federal power is "few and defined" against a "numerous and indefinite" state residue.

St. George Tucker's 1803 annotation of Blackstone catalogs Art. I sec. 10's prohibitions on the states as the outer limit on state power and treats everything else — including "the right of property" and most "rights of persons" — as retained by the states. Tucker frames the states as still "sovereign," "independent," and merely suspending (not surrendering) the "exercise of the rights of sovereignty" for the duration of the Union — language that anticipates the later compact-theory and nullification arguments recorded on Compact Theory.

Story's Commentaries §§ 1900–1901 (1833) confirm that the clause is declaratory rather than restrictive, and expressly rejects reading it to cut down implied powers:

"This amendment is a mere affirmation of what, upon any just reasoning, is a necessary rule of interpreting the constitution. Being an instrument of limited and enumerated powers, it follows irresistibly, that what is not conferred, is withheld ... All powers not delegated, (not all powers not expressly delegated,) and not prohibited, are reserved." — Joseph Story, Commentaries on the Constitution 3:§§ 1900–1901, 1833

James Monroe's 1822 message on internal improvements applies the same original allocation practically: the federal government's powers are "enumerated and defined in the most precise form," while the states retain the general residue — territory, militia organization, "descents, contracts, and all the concerns of private property," and "the whole criminal code" outside federal jurisdiction.

The Massachusetts convention: the amendment's floor-tested ancestor, fourteen months before Congress

The wiki's earliest floor reading of language that became the Tenth Amendment is not the First Congress's 1789 debate (above) but the Massachusetts ratifying convention's, on 1 February 1788 — more than a year before Madison introduced any amendments in the House. Gov. Hancock's conciliatory proposition, submitted 31 January to break the convention's deadlock (see Amendment Process Clause for the full episode), opened with exactly this reserved-powers principle as its first recommended amendment. Hon. Mr. Samuel Adams read it into his own speech the next day, word for word:

"Your excellency's first proposition is, 'that it be explicitly declared, that all powers not expressly delegated to Congress are reserved to the several states, to be by them exercised.' This appears, to my mind, to be a summary of a bill of rights, which gentlemen are anxious to obtain." — Hon. Mr. Adams, Massachusetts Convention, 1 Feb. 1788

Adams's own gloss on the proposition — before any of the 1789 congressional debate over the word "expressly" (above) — already ties it to the Confederation's own reserved-powers clause, and to judicial enforcement of the limit it states:

"It is consonant with the second article in the present Confederation, that each state retains its sovereignty, freedom, and independence, and every power, jurisdiction, and right, which is not, by this Confederation, expressly delegated to the United States in Congress assembled." — Hon. Mr. Adams, Massachusetts Convention, 1 Feb. 1788

Adams's proposed amendment, unlike the ratified Tenth Amendment, still carries the word "expressly" — the same word Madison and Sherman would argue out of the First Congress's text nineteen months later (above). The Massachusetts convention's own text is therefore direct evidence that the "expressly"-qualified reading was not a straw position invented in 1789: it was the form in which the reserved-powers principle first reached the floor of a ratifying body, and the First Congress's choice to drop the word was a considered departure from this exact precedent, not merely from the Confederation's Article II.

Dr. Jarvis, defending the whole slate of Hancock's amendments against the objection that the convention had no authority to propose any, singled out this first article as the one that answered the bill-of-rights objection entirely on its own:

"When we talk of our wanting a bill of rights to the new Constitution, the first article proposed must remove every doubt on this head; as, by positively securing what is not expressly delegated, it leaves nothing to the uncertainty of conjecture, or to the refinements of implication, but is an explicit reservation of every right and privilege which is nearest and most agreeable to the people." — Dr. Jarvis, Massachusetts Convention, 4 Feb. 1788

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Adams's and Jarvis's speeches predate every other founding-era source already on this page — Madison's Federalist No. 45 (26 Jan. 1788, five days earlier, but a general allocation argument rather than a specific amendment text), Iredell's North Carolina proposal (Aug. 1788), and the First Congress's own debate (Aug. 1789) — by between six months and nineteen months. Massachusetts did not condition ratification on this or any other amendment (see Amendment Process Clause for the Massachusetts Compromise's "ratify now, amend later" structure), so Adams's and Jarvis's speeches are best read as the amendment's floor-tested rhetorical ancestor rather than as binding constitutional text in their own right — but they establish that the reserved-powers-with-"expressly" formula, later rejected by the First Congress, was already fully formed, already understood as "a summary of a bill of rights," and already treated as a live proposal fourteen months before Congress took the question up.

The ratification instrument's own text, and a wording variance from Adams's floor reading

The convention approved Gov. Hancock's proposition and ratified 6 February 1788 by 187-168, then had Elliot record the ratification instrument itself — the document actually transmitted to Congress, distinct from any delegate's paraphrase of it on the floor. Its first recommended amendment states the reserved-powers principle in the instrument's own words:

"First. That it be explicitly declared, that all powers not expressly delegated by the aforesaid Constitution are reserved to the several states, to be by them exercised." — Massachusetts ratification instrument, 6-7 Feb. 1788

This text is close to, but not identical with, Samuel Adams's floor reading of the same proposition five days earlier (above), which the wiki already carries as "all powers not expressly delegated to Congress are reserved to the several states, to be by them exercised." The instrument's finished text reads "not expressly delegated by the aforesaid Constitution" — a shift from delegation to an institution to delegation by the founding document itself, closer to the Tenth Amendment's own eventual "not delegated to the United States by the Constitution" phrasing than Adams's earlier floor wording was.

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The variance is minor but not nothing: it shows the amendment's language was still being settled between the proposition's 31 January introduction and its final 6-7 February transmittal text, even though the underlying "expressly delegated" reserved-powers principle stayed constant throughout. The First Congress's 1789 text (above) drops "expressly" from both formulations — a substantive change Madison and Sherman argued for on the House floor — but keeps the instrument's "by the Constitution" framing over Adams's "to Congress" framing, suggesting the finished Massachusetts text, not the floor paraphrase, is the closer textual ancestor of the ratified Amendment.

A post-ratification restatement: the Harrisburg conference, September 1788

Massachusetts's "expressly delegated" formula (above) was not the last ratification-era restatement before the First Congress took the question up. Nine months after Pennsylvania ratified, twenty-seven of that convention's Anti-Federalist opponents met at Harrisburg and petitioned the state legislature for a second general convention, proposing their own reserved-powers amendment as the first of twelve, keyed to a specific clause rather than offered as free-standing text:

"That Congress shall not exercise any powers whatever, but such as are expressly given to that body by the Constitution of the United States: nor shall any authority, power, or jurisdiction, be assumed or exercised by the executive or judiciary departments of the Union, under color or pretence of construction or fiction; but all the rights of sovereignty, which are not by the said Constitution expressly and palinly vested in the Congress, shall be deemed to remain with, and shall be exercised by, the several states in the Union . . ." — Harrisburg Conference, proposed amendment I, 3 Sept. 1788, quoted in Elliot's Debates vol. 2

Unlike Massachusetts's instrument, the Harrisburg petition came from a minority that had already lost its convention fight and carried no ratification leverage — it is evidence that the "expressly"-qualified formula remained the default Anti-Federalist demand up to a year after the Constitution's first state ratifications, not that it commanded any institutional assent beyond its own signers. See Elliot's Debates (Vol. II).

Mason demands an express reserved-powers clause; Nicholas's "thousand acres" answer; Henry's inversion argument

Fourteen months before Gov. Hancock's Massachusetts proposition (above) reached print as a ratification instrument, and thirteen months before the same formula surfaced again in the Virginia convention as a specific floor demand, George Mason pressed the identical principle at Richmond on 14 June 1788 — not as an amendment text yet, but as an argument that the Constitution's silence on retained powers was itself a defect the Necessary and Proper Clause's own defenders (see Necessary and Proper Clause) had not answered:

"Is there any thing in this Constitution which secures to the states the powers which are said to be retained? Will powers remain to the states which are not expressly guarded and reserved?... I wish a clause in the Constitution, with respect to all powers which are not granted, that they are retained by the states. Otherwise, the power of providing for the general welfare may be perverted to its destruction." — George Mason, Virginia Convention, 14 June 1788

Mason located the same demand in the Confederation's own Article II, arguing the new Constitution needed the reserved-powers clause even more urgently than the government it replaced, given the "great augmentation of power" the new plan vested in the general government:

"There was a clause in the Confederation reserving to the states respectively every power, jurisdiction, and right, not expressly delegated to the United States. This clause has never been complained of, but approved by all. Why not, then, have a similar clause in this Constitution... Unless there be some express declaration that every thing not given is retained, it will be carried to any power Congress may please." — George Mason, Virginia Convention, 14 June 1788

George Nicholas answered with a property analogy this wiki's Tenth Amendment record does not otherwise carry, reasoning that an express reservation is logically unnecessary once a grant is understood to convey only what it states:

"It is agreed upon by all that the people have all power. If they part with any of it, is it necessary to declare that they retain the rest?... If I have one thousand acres of land, and I grant five hundred acres of it, must I declare that I retain the other five hundred? Do I grant the whole thousand acres, when I grant five hundred, unless I declare that the five hundred I do not give belong to me still? It is so in this case. After granting some powers, the rest must remain with the people." — George Nicholas, Virginia Convention, 14 June 1788

Patrick Henry, opening the convention's 9th-section review the next day, gave the objection its sharpest form yet in this wiki's record — arguing the Constitution's specific, limited list of negative restrictions (Art. I sec. 9) proves the default rule runs backward from what Nicholas's and Randolph's enumerated-powers theory (see Necessary and Proper Clause) claims:

"It reverses the position of the friends of this Constitution, that every thing is retained which is not given up; for, instead of this, every thing is given up which is not expressly reserved... If the power remains with the people, how can Congress supply the want of an affirmative grant? They cannot do it but by implication, which destroys their doctrine." — Patrick Henry, Virginia Convention, 15 June 1788

Henry pressed the same inversion with an English-law comparison distinct from any already on this page, arguing every nation that has faced the same construction question has resolved it against the silent citizen, not for him:

"I repeat, that all nations have adopted this construction — that all rights not expressly and unequivocally reserved to the people are impliedly and incidentally relinquished to rulers, as necessarily inseparable from the delegated powers. It is so in Great Britain; for every possible right, which is not reserved to the people by some express provision or compact, is within the king's prerogative." — Patrick Henry, Virginia Convention, 15 June 1788

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Mason's and Henry's demand and Nicholas's "thousand acres" answer are the same reserved-powers dispute this page already traces through Massachusetts's Gov. Hancock proposition (1 Feb. 1788, above) and the First Congress's 1789 "expressly" debate — argued a year earlier, on the floor that would go on to make Virginia's own ratification instrument (26 June 1788) the first to write "every power not granted thereby remains with them, and at their will" directly into a state's ratification text (see Bill of Rights). Nicholas's land-grant analogy is this wiki's only property-law argument for the reserved-powers default rule; every other source on this page argues from constitutional structure or from the Confederation's own precedent.

George Nicholas's ratification-language argument, and Madison's "unnecessary and dangerous" objection to a bill of rights (24 June 1788)

Ten days after Mason's and Henry's floor demand for an express reserved-powers clause (above), the Virginia convention reached the same principle again from a different direction — not as a proposed constitutional amendment, but as language to write directly into Virginia's own instrument of ratification, answering George Wythe's 24 June motion to ratify with recommendatory rather than conditional amendments (see Amendment Process Clause and George Wythe). George Nicholas argued the ratification instrument's own reservation language already secured everything a separate bill of rights would:

"[T]he language of the proposed ratification would secure every thing which gentlemen desired, as it declared that all powers vested in the Constitution were derived from the people, and might be resumed by them whensoever they should be perverted to their injury and oppression; and that every power not granted thereby remained at their will... In like manner these conditions will be binding on Congress. They can exercise no power that is not expressly granted them." — Elliot's summary of George Nicholas, Virginia Convention, 24 June 1788

James Madison closed the exchange with the convention's most direct statement of the case against a separate bill of rights, resting on the same enumerated-powers logic Nicholas's own 10 June "sweeping clause" speech (see Necessary and Proper Clause) had already given for the Necessary and Proper Clause specifically — here generalized into the founding era's clearest "unnecessary and dangerous" formula, later echoed by Hamilton's *Federalist* No. 84:

"[W]hat defects might be in the Constitution might be removed by the amendatory mode in itself. As to a solemn declaration of our essential rights, he thought it unnecessary and dangerous — unnecessary, because it was evident that the general government had no power but what was given it, and that the delegation alone warranted the exercise of power; dangerous, because an enumeration which is not complete is not safe. Such an enumeration could not be made, within any compass of time, as would be equal to a general negation, such as his honorable friend (Mr. Wythe) had proposed." — Elliot's summary of James Madison, Virginia Convention, 24 June 1788

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Nicholas's and Madison's arguments here answer the reserved-powers demand structurally rather than textually — not by drafting a clause like Mason's or Henry's (above), but by reading the ratification instrument's own reservation language, and the enumerated-powers default rule itself, as already doing a bill of rights's work. Virginia's actual ratification instrument, adopted the next day (26 June 1788, see Bill of Rights), carries almost exactly the reservation language Nicholas describes here — direct evidence the convention majority agreed with Nicholas's reading over Mason's and Henry's insistence on a separate, express textual guarantee.

The Virginia Instrument of Ratification, and Wythe's proposed amendment I (25-27 June 1788)

Nicholas's 24 June paraphrase (above) is confirmed almost word for word by the ratification instrument Virginia actually adopted the next day. Gov. Edmund Randolph, reporting from the ratification committee, read the instrument's operative reservation clause into the record:

"...Do, in the name and in behalf of the people of Virginia, declare and make known, that the powers granted under the Constitution, being derived from the people of the United States, be resumed by them whensoever the same shall be perverted to their injury or oppression, and that every power, not granted thereby, remains with them, and at their will; that, therefore, no right, of any denomination, can be cancelled, abridged, restrained, or modified, by the Congress, by the Senate or House of Representatives, acting in any capacity, by the President, or any department or officer of the United States, except in those instances in which power is given by the Constitution for those purposes; and that, among other essential rights, the liberty of conscience and of the press cannot be cancelled, abridged, restrained, or modified, by any authority of the United States." — Virginia Instrument of Ratification, adopted 25 June, engrossed and signed 26-27 June 1788

Virginia's own committee resolution, read to the convention before the ratification vote itself, states the identical "gift of the people" premise in near-identical language, showing the reservation principle was settled convention business rather than last-minute drafting:

"Whereas the powers granted under the proposed Constitution are the gift of the people, and every power not granted thereby remains with them, and at their will..." — committee resolution, Virginia Convention, 25 June 1788

Two days later, Mr. Wythe's committee reported the "AMENDMENTS TO THE CONSTITUTION" the convention recommended to the first Congress — twenty-one articles opening with the reserved-powers principle restated as proposed federal constitutional text, distinct from both the ratification instrument's preamble and Mason's and Henry's 14-15 June floor demands (above), and the closest textual ancestor on this page to the Amendment's eventual "reserved to the States respectively, or to the people" phrasing:

"1st. That each state in the Union shall respectively retain every power, jurisdiction, and right, which is not by this Constitution delegated to the Congress of the United States, or to the departments of the federal government." — Virginia Convention, proposed amendment I, 27 June 1788

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This page now carries the reserved-powers principle in four distinct ratification-era forms from the same Virginia convention within a two-week span: Mason's and Henry's floor demand for an express clause (14-15 June), Nicholas's ratification-instrument argument and Madison's "unnecessary and dangerous" reply (24 June), the ratification instrument's own adopted text (25-27 June, above), and Wythe's committee's proposed constitutional amendment (27 June, above). The instrument's text and the proposed amendment's text differ in register — the instrument frames reservation as a condition of Virginia's own assent ("the powers granted... be resumed by them"), while the proposed amendment frames it as freestanding constitutional text for all states ("each state... shall respectively retain") — but both descend from the same "gift of the people" premise Nicholas argued on the floor.

Modern doctrine departure

The Tenth Amendment's original function — a rule confirming that ungranted power stays with the states, not an independent limit on how Congress may use its granted powers — has been read at different points in tension with an expanding view of implied and resulting federal power (see Enumerated powers). Twentieth-century doctrine has cycled between treating the amendment as "but a truism" and reviving it as a structural constraint: National League of Cities v. Usery found an affirmative Tenth Amendment limit on Congress's Commerce power over state employment, Garcia v. San Antonio Metropolitan Transit Authority overruled that holding and returned to the procedural-safeguards view, and Printz v. United States later revived a structural anti-commandeering rule barring Congress from conscripting state executive officers. The debate over whether the Tenth Amendment does independent constitutional work, or merely restates the enumerated-powers premise Madison and Story both describe, remains unsettled — see Federalism.

Modern doctrine (Annotated Constitution, Amdt10.1-10.4.2)

Early jurisprudence. In McCulloch v. Maryland (1819), Chief Justice Marshall rejected the argument that the Tenth Amendment — unlike Article II of the Articles of Confederation, which reserved to the states everything not "expressly" delegated — denied the federal government implied or incidental powers. The Amendment's effect, rather, is to leave the question "whether the particular power which may become the subject of contest has been delegated to the one government, or prohibited to the other, to depend upon a fair construction of the whole instrument."

State police-power era. In the early twentieth century, the Court relied on the Tenth Amendment alongside a narrow reading of the Commerce Clause to invalidate federal economic regulation as invasive of the states' reserved police powers. Hammer v. Dagenhart (1918), invalidating a federal ban on interstate shipment of goods made with child labor, is the leading example: "to them and to the people the powers not expressly delegated to the national government are reserved." A parallel line of cases in the same period upheld federal laws penalizing interstate transport of lottery tickets, women for immoral purposes, stolen cars, and diseased cattle — tension the Court did not resolve until the New Deal era.

The Darby reversal. Beginning in 1937, the Court retreated from Hammer's conception of the Amendment. United States v. Darby (1941) expressly overruled Hammer, holding the Tenth Amendment "states but a truism that all is retained which has not been surrendered" and imposes no independent substantive limit on Congress's enumerated powers.

State sovereignty era. Beginning in the mid-1970s, the Court used the Tenth Amendment to analyze congressional intrusions on state sovereignty rather than mere police power. National League of Cities v. Usery (1976) held Congress could not use the Commerce Clause to displace states' control of "integral" or "traditional" governmental functions, such as the wages paid to their own employees — even though the underlying regulation was "undoubtedly within the scope of the Commerce Clause." Garcia v. San Antonio Metropolitan Transit Authority (1985) overruled National League of Cities nine years later as "unworkable" and "doctrinally barren," holding states must look primarily to the political process, not judicial line-drawing, for protection against Congress's use of the commerce power — while allowing that some "affirmative limits the constitutional structure might impose on federal action affecting the States" might still exist.

Anti-commandeering doctrine. Beginning in the 1990s the Court began identifying those affirmative limits. New York v. United States (1992) held Congress may not commandeer state legislatures by compelling them to enact or administer a federal regulatory program, reasoning that "[t]he Constitution does not protect the sovereignty of States for the benefit of the States or State governments, [but instead] for the protection of individuals" — so state officials cannot consent to an enlargement of congressional power. Printz v. United States (1997) extended the rule to bar Congress from conscripting state executive officers directly, striking the Brady Act's background-check mandate on state and local law enforcement. Gregory v. Ashcroft (1991) had already signaled the retreat from Garcia's political-safeguards approach by adopting a "clear statement" rule requiring an unambiguous statement of congressional intent before a federal law is read to displace core state authority. Reno v. Condon (2000) marked the anti-commandeering line's outer limit, upholding a federal law restricting resale of state motor-vehicle records because it regulated the states "as the owners of databases" rather than commandeering their regulatory processes over private parties. NFIB v. Sebelius (2012) extended anti-commandeering logic to the spending power, holding a spending condition that leaves a state "no choice" is unconstitutionally coercive in the same way outright commandeering would be — the Medicaid-expansion holding this wiki already documents from the Taxing and Spending Clause angle, now cross-referenced to its structural anti-commandeering framing. Murphy v. NCAA (2018) applied the rule to bar Congress from prohibiting state legislatures from repealing their own sports-gambling prohibitions, because the anti-commandeering rule reaches prohibitions on state action as much as affirmative commands — the distinction between the two is "empty." Haaland v. Brackeen (2023) is the most recent application, and confirms the doctrine's "evenhandedness" limit reaches state courts: the Court rejected the argument that the Indian Child Welfare Act's placement-preference and "active efforts" requirements commandeer state courts and officials, reasoning that "[l]egislation that applies evenhandedly to state and private actors does not typically implicate the Tenth Amendment," since state agencies or private parties could equally initiate the proceedings ICWA governs, and that Congress may require state courts to enforce federal law without commandeering them.

Equal sovereignty doctrine. South Carolina v. Katzenbach (1966) first stated the equal-sovereignty principle narrowly, observing that "[t]he doctrine of the equality of States . . . applies only to the terms upon which States are admitted to the Union." Northwest Austin Municipal Utility District Number One v. Holder (2009) applied the principle more broadly to the Voting Rights Act's Section 4 coverage formula and Section 5 preclearance requirement, finding they impose "substantial federalism costs" that had become harder to justify given changed conditions since 1965 and that the formula's disparate treatment of states departed from "the fundamental principle of equal sovereignty" — but the Court resolved the case on statutory grounds rather than reaching the constitutional question. Four years later Shelby County v. Holder (2013) reached that question, holding "a departure from the fundamental principle of equal sovereignty requires a showing that a statute's disparate geographic coverage is sufficiently related to the problem that it targets," and striking the coverage formula because "things have changed dramatically" in the nearly fifty years since Katzenbach upheld it. The Court has not decided an equal-sovereignty challenge since Shelby County, and it remains unclear whether or how the doctrine applies outside the voting-rights context.

Commerce Clause and Tenth Amendment. United States v. Lopez (1995) struck down a federal ban on gun possession near schools, rejecting the argument that its economic effects brought it within the Commerce Clause; accepting that rationale, the Court said, would eliminate the "distinction between what is truly national and what is truly local," converting the commerce power into "a general police power of the sort retained by the states" and undermining "the first principle that the federal government is one of enumerated and limited powers." United States v. Morrison (2000) applied the same principle to invalidate the Violence Against Women Act's federal civil remedy for gender-motivated violence, holding Congress may not regulate "noneconomic, violent criminal conduct based solely on that conduct's aggregate effect on interstate commerce": "[w]e can think of no better example of the police power, which the Founders denied the National Government and reposed in the States, than the suppression of violent crime and vindication of its victims." Gonzales v. Raich (2005) went the other way, upholding Congress's power to prohibit intrastate cultivation and use of medical marijuana based on its aggregate effect on interstate commerce; the majority distinguished Lopez and Morrison as regulations of noneconomic activity and referenced the Tenth Amendment only obliquely, through a citation to United States v. Darby, while Justice O'Connor's dissent invoked it directly, arguing the ruling "unconstitutionally encroached on state police powers." NFIB v. Sebelius (2012) held the Commerce Clause could not be used to compel individuals to engage in commercial activity — placing the Affordable Care Act's individual mandate beyond that power (though the Court ultimately upheld it under the taxing power) — and along the way cautioned that Congress's enumerated powers "must be read carefully to avoid creating a general federal authority akin to the police power," invoking the Tenth Amendment and related federalism principles.