The Tenth Amendment to the Constitution defines 10th Amendment state powers by reserving to the states, or to the people, every power that the Constitution does not hand to the federal government or forbid to the states. Ratified in 1791 as part of the Bill of Rights, it confirms the structural bargain of the whole document: Washington gets only the authority the Constitution grants it, and everything else stays closer to home.
The full text is a single sentence: “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.”1Congress.gov. U.S. Constitution – Tenth Amendment That sentence does three things. Federal power has to come from a delegation somewhere in the Constitution’s text. The Constitution also strips certain powers from the states directly (Article I, Section 10 bars states from coining money or entering treaties, for example). Everything left over belongs either to the states or to the people.
What Powers Do States Actually Keep
Where federal power runs out, state authority begins. States hold what constitutional law calls the police power, a general ability to regulate for the public good that doesn’t depend on any specific constitutional grant. The Supreme Court has described it as covering public safety, public health, morality, and general welfare. A state doesn’t need to point to a particular clause in a founding document before it passes a law. That inherent sovereignty is what the Tenth Amendment protects.
This is why states, not the federal government, set the rules for most of daily life. Building codes. Professional licensing for doctors and lawyers. Speed limits. Zoning. Criminal law. Public education. Vaccination requirements for school attendance. All of these flow from state police power. The federal government has no general authority to legislate on these subjects unless it can tie the legislation to an enumerated power such as the Commerce Clause or the Spending Clause.
Police power is broad but not unlimited. The Fourteenth Amendment’s Due Process and Equal Protection Clauses prevent states from exercising this authority in ways that violate individual rights, and other constitutional protections apply against the states as well.
The Federal Side of the Line
Article I, Section 8 lists the specific jobs Congress can do: levy taxes, borrow money, regulate commerce among the states, coin currency, declare war, maintain armed forces, establish post offices, and about a dozen more.2Constitution Annotated. Article I Section 8 – Enumerated Powers These enumerated powers mark the outer boundary of legitimate federal legislation. Every federal law, in theory, must trace back to one of them. If it can’t, the Tenth Amendment says that power belongs to the states or the people.
The boundary has always been blurrier than a clean list suggests. The last clause of Section 8 gives Congress the power “to make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers.”3Constitution Annotated. Overview of Necessary and Proper Clause That Necessary and Proper Clause lets Congress do things not explicitly listed, as long as those actions are a reasonable means of carrying out an enumerated power. It is not an independent grant of authority, but “necessary” has been read broadly enough that Congress usually only needs to show a rational connection.
The Commerce Clause and Its Limits
No enumerated power has generated more Tenth Amendment conflict than the Commerce Clause, which gives Congress authority to regulate commerce “among the several States.” For most of the twentieth century, the Supreme Court read that power expansively, upholding federal regulation of activities with even a remote connection to interstate commerce.
In United States v. Lopez (1995), the Court drew a line. Congress had made it a federal crime to possess a firearm within 1,000 feet of a school, and the Court struck the law down because carrying a gun near a school is not an economic activity that substantially affects interstate commerce.4Justia U.S. Supreme Court. United States v. Lopez, 514 U.S. 549 (1995) Lopez set out three categories the Commerce Clause reaches: the channels of interstate commerce, the instrumentalities of interstate commerce, and activities that substantially affect interstate commerce. Anything outside those categories belongs to the states.
What Congress Cannot Do to States
One of the Tenth Amendment’s most concrete protections is the anti-commandeering doctrine: the federal government cannot order state governments to carry out federal policy. States are independent political entities, not branch offices of Washington. Three Supreme Court cases built the rule.
In New York v. United States (1992), Congress tried to force states to either regulate radioactive waste according to federal standards or take legal ownership of the waste themselves. The Court struck down the “take title” provision, holding that Congress can encourage states through incentives and can regulate private individuals directly, but cannot order state legislatures to pass specific laws.5Justia U.S. Supreme Court. New York v. United States, 505 U.S. 144 (1992)
Printz v. United States (1997) extended the principle to state executive officials. The Brady Handgun Violence Prevention Act required local law enforcement officers to conduct background checks on gun purchasers as an interim measure. The Court held that Congress cannot conscript state officers to administer a federal regulatory program, no matter how minimal or mechanical the task.6Justia U.S. Supreme Court. Printz v. United States, 521 U.S. 898 (1997) If Washington wants background checks, it has to use its own agents.
Murphy v. NCAA (2018) closed a gap. A federal law had prohibited states from authorizing sports gambling. The statute didn’t order states to ban sports betting; it told them they couldn’t lift existing bans. The Court held that distinction was meaningless. Whether Congress compels a state legislature to act or prohibits it from acting, the result is the same: Congress dictates what a state legislature may and may not do, which “is as if federal officers were installed in state legislative chambers.”7Supreme Court of the United States. Murphy v. National Collegiate Athletic Association The ruling opened the door for states to legalize sports betting on their own terms.
Anti-commandeering also serves political accountability. When Washington forces states to implement a federal policy, voters may blame state officials for a program those officials didn’t choose. Keeping the lines clear means citizens know which level of government is responsible for which decisions.
When Federal Money Comes With Strings
The federal government can’t command states, but it can pay them to cooperate. Congress routinely attaches conditions to federal grants. Highway money comes with a required drinking age of 21. Education funding comes with testing mandates. The Supreme Court approved this approach in South Dakota v. Dole (1987), setting out when conditions on federal spending are constitutional.8Justia U.S. Supreme Court. South Dakota v. Dole, 483 U.S. 203 (1987)
Under Dole, conditions on federal funds must serve the general welfare, be stated clearly enough for states to understand what they are agreeing to, have a reasonable connection to the federal program being funded, and not require states to do something that would violate another constitutional provision. The Court also acknowledged a fifth, implicit limit: at some point a financial incentive becomes so large that it stops being encouragement and turns into coercion.
That coercion limit finally bit in National Federation of Independent Business v. Sebelius (2012), the challenge to the Affordable Care Act. The ACA expanded Medicaid eligibility and threatened to cut off all existing Medicaid funding to any state that refused to participate. The Court held that this was not a reasonable condition. In the Chief Justice’s words, it was “a gun to the head.”9Justia U.S. Supreme Court. National Federation of Independent Business v. Sebelius, 567 U.S. 519 (2012) Because Medicaid represented over 10 percent of most state budgets, the threatened loss left states with no real choice. Congress could offer the new Medicaid money with strings attached, but could not yank away existing funding as punishment for declining.
Where Federal Law Still Wins
The Tenth Amendment’s reservation of power to the states runs into Article VI, the Supremacy Clause: “This Constitution, and the Laws of the United States which shall be made in Pursuance thereof . . . shall be the supreme Law of the Land.”10Congress.gov. U.S. Constitution – Article VI When a valid federal law conflicts with a state law, the federal law wins. This is preemption, and it is the primary way federal authority overrides state law that would otherwise be protected by the Tenth Amendment.
Preemption takes two forms. Express preemption is where Congress explicitly states in a statute that federal law overrides state law on a particular subject. Implied preemption occurs when a federal scheme is so comprehensive that it leaves no room for state regulation, or when compliance with both federal and state law is physically impossible. Either way, the state law gives way.
The Tenth Amendment doesn’t prevent preemption, but it does shape how courts read ambiguous federal statutes. When Congress hasn’t clearly spoken, courts generally presume that traditional state authority survives.
Who Can Raise a Tenth Amendment Claim
For years, most federal courts held that only states could bring Tenth Amendment challenges, on the theory that the amendment protected the structural relationship between governments rather than individual rights. The Supreme Court rejected that view in Bond v. United States (2011). A woman charged under a federal chemical weapons statute argued that the law exceeded Congress’s enumerated powers and intruded on state authority. The Court held that she had standing to make the argument, reasoning that “federalism secures to citizens the liberties that derive from the diffusion of sovereign power.”11Legal Information Institute. Bond v. United States
The individual still needs to meet the ordinary requirements for bringing a lawsuit, including a concrete and particular injury caused by the challenged law. But the Tenth Amendment is no longer a tool only state attorneys general can pick up.
How Courts Have Interpreted the Amendment Over Time
The Tenth Amendment’s force as a legal constraint has waxed and waned. For most of the twentieth century it was treated as largely symbolic. In United States v. Darby (1941), the Court called it “but a truism that all is retained which has not been surrendered,” meaning it restates the Constitution’s design rather than adding to it.12Constitution Annotated. Tenth Amendment and Darby The Commerce Clause and Necessary and Proper Clause expanded so broadly that federal authority seemed to reach almost everywhere.
Starting in the 1990s, the Rehnquist Court revived federalism limits through a different route: not by defining which state functions are protected, but by identifying what Congress cannot do. New York v. United States built the anti-commandeering doctrine. Lopez placed limits on the Commerce Clause. Printz extended anti-commandeering to state executive officers. NFIB v. Sebelius found a coercion ceiling on the spending power, and Murphy v. NCAA confirmed that Congress cannot bar states from changing their own laws.13Constitution Annotated. Tenth Amendment – Rights Reserved to the States and the People
The modern Tenth Amendment isn’t the blank check it was in the pre-New Deal era, and it isn’t the empty truism it was for much of the mid-twentieth century. It sits in a middle ground. Federal enumerated powers remain broad, but the methods Congress uses to exercise them face real constraints. States can’t nullify federal law, and they can’t be drafted into enforcing it either. Where the boundary falls in any given case depends on which enumerated power Congress is invoking, how directly the law regulates state governments, and whether the Court sees the federal action as cooperation or coercion.