What does the United States 10th amendment say?

1. What the text says — the amendment itself

The amendment’s exact 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”—is unanimous across primary sources and official repositories including the Library of Congress and the National Archives, and that single sentence is the full substance of the Tenth Amendment ^{[1] [4] [3]}.

2. Why it was added — historical context and ratification

The Tenth Amendment was adopted December 15, 1791 as the last clause of the Bill of Rights to reassure states and anti‑Federalists that powers not expressly given to the national government would remain with states or the people; scholars note it emerged from the fraught ratification debates and proposals from state conventions that wanted a clear reservation of powers ^{[2] [5] [3]}.

3. Plain meaning and the architecture of federalism

At face value the amendment expresses federalism: federal powers are limited to those delegated by the Constitution and residual authority lies with states or the people, a principle taught in education and legal primers which describe the Tenth Amendment as reserving unspecified powers to states or people whenever the Constitution is silent ^{[6] [7] [5]}.

4. Judicial treatment — from “tautology” to a revived tool

Courts have treated the amendment variably: some Supreme Court decisions and scholars call it a “truism” or “tautology,” arguing its force is limited because it merely restates that the federal government has only enumerated powers, while other decisions—most notably New York v. United States and subsequent “New Federalism” cases—have given it sharper bite by blocking certain federal coercive actions against states; legal commentary records both approaches and cautions that the amendment’s practical effect often depends on broader constitutional interpretation ^{[8] [9] [10]}.

5. How the Tenth Amendment functions in practice and politics today

Practically, the amendment is a frequent basis for litigation and political claims: states invoke it to challenge federal programs or actions and Congress and the courts have alternately upheld and limited federal power in regulatory, taxing, and coercive contexts—legal anthologies and Congressional materials document cases where the Tenth Amendment was cited in disputes over federal taxation, regulatory reach, and state obligations, and recent legislative proposals like the “10th Amendment Restoration Act of 2025” show its continued political currency ^{[11] [10] [12] [9]}.

6. Limits, disagreements, and takeaways

Interpretive disputes remain fundamental: some view the amendment as a structural reminder with little standalone judicial force—“not derived from its text,” as one analysis puts it—while others treat it as an active constitutional check on federal overreach; authoritative sources underline that whether a power is “delegated” or “reserved” often depends on broader constitutional construction and case law rather than the single sentence of the amendment itself ^{[8] [9] [13]}.