The Tenth Amendment is the closing provision of the Bill of Rights, and it sets the default rule for American federalism: any power the Constitution does not hand to the federal government, and does not forbid to the states, belongs to the states or to the people. Its 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.”1Library of Congress. U.S. Constitution – Tenth Amendment Ratified in 1791, those 28 words still decide who can regulate what.
What the Text Actually Does
Three ideas sit inside the sentence. The federal government has only the powers the Constitution gives it. The Constitution separately forbids states from doing certain things, like coining their own money. Everything left over defaults to the states or to individual citizens, automatically, without any federal law or order needed to activate it.
That default matters because it flips the burden of justification. A state does not need to point to a constitutional clause before it acts. Congress does.
Enumerated Federal Powers
Congress can legislate only when it can identify a specific grant of authority in the constitutional text. The Commerce Clause lets it regulate trade across state lines. The Taxing and Spending Clause lets it collect taxes and spend for the general welfare. The Necessary and Proper Clause gives it room to pass laws that carry those listed powers into effect.2Legal Information Institute. Enumerated Powers Other explicit grants include the power to coin money3Congress.gov. Article I Section 8 Clause 5 and the power to declare war.4Congress.gov. Article I Section 8 Clause 11 If no enumerated grant covers a subject, the federal government has no constitutional foothold there.
What States Keep: The Police Power
The flip side of limited federal power is broad state authority. States hold what lawyers call the “police power,” a general capacity to legislate for the health, safety, welfare, and morals of their residents. It is inherent rather than delegated, and it fills most of the space where the federal government cannot reach.
Education runs on it. States create school districts, set curriculum standards, fund public universities, and enforce compulsory attendance. Property regulation runs on it too: zoning, land use permits, building codes, and the recording of deeds all operate under state law. Family law, including marriage, divorce, and child custody, is almost entirely a state domain. Professional licensing for doctors, lawyers, electricians, and dozens of other occupations flows from the same source, with state boards setting standards, administering exams, and pulling credentials for violations.
State police power also reaches public health emergencies. Quarantine orders, isolation requirements, and mandatory vaccination programs during outbreaks all rest on this authority. It is broad, not unlimited: any state action still has to respect individual constitutional rights, including those the Fourteenth Amendment makes enforceable against states.
The Anti-Commandeering Doctrine
The sharpest modern use of the Tenth Amendment is the anti-commandeering doctrine. It does not ask whether Congress may regulate a subject. It asks how Congress goes about it. The rule: Congress cannot order state legislatures to pass laws, and it cannot draft state or local officials into carrying out federal programs.5Congress.gov. Amdt10.4.2 Anti-Commandeering Doctrine If the federal government wants something done, it has to do it with federal personnel, or persuade states to cooperate. Three cases built the doctrine.
New York v. United States (1992)
A federal statute on low-level radioactive waste told states that if they missed a disposal deadline, they had to take title to the waste and accept liability for damage it caused. The Court struck the provision down, holding that Congress cannot “commandeer state governments into the service of federal regulatory purposes.”6Justia U.S. Supreme Court Center. New York v. United States The concern was accountability. If state officials are forced to run a federal program, voters cannot tell whom to blame when it fails.
Printz v. United States (1997)
The Brady Handgun Violence Prevention Act required local law enforcement officers to run background checks on handgun buyers while the federal government built a national system. Two sheriffs sued and won. The Court held the federal government “may not compel the States to enact or administer a federal regulatory program,” and that federal power “would be augmented immeasurably and impermissibly if it were able to impress into its service—and at no cost to itself—the police officers of the 50 States.”7Legal Information Institute. Printz v. United States Printz extended the anti-commandeering rule from state legislatures to state and local executive officials.
Murphy v. NCAA (2018)
The most recent expansion involved the Professional and Amateur Sports Protection Act, which barred states from authorizing sports gambling. New Jersey repealed its own ban, the NCAA sued, and the Court sided with New Jersey. It held that “the distinction between compelling a State to enact legislation and prohibiting a State from enacting new laws is an empty one. The basic principle—that Congress cannot issue direct orders to state legislatures—applies in either event.”8Supreme Court of the United States. Murphy v. National Collegiate Athletic Association Congress cannot commandeer by telling states what to do, and it cannot commandeer by telling them what they are forbidden to do either.
Federal Spending and the Coercion Line
Congress cannot order states around, but it can offer them money with conditions attached, and that is how most federal influence over state policy actually works. Highway funds, education funds, Medicaid funds all come with strings. States that want the money follow the strings.
In South Dakota v. Dole (1987), the Court set out four requirements for conditional grants. The spending must serve the general welfare. The conditions must be clear enough that states know what they are agreeing to. The conditions must relate to the federal interest in the program being funded. And the conditions cannot violate other constitutional provisions.9Justia U.S. Supreme Court Center. South Dakota v. Dole The condition in that case was a 5% cut of federal highway funds for states that kept their drinking age below 21. That amount came to less than half of one percent of South Dakota’s budget, and the Court called it a nudge rather than a shove.
The shove came in NFIB v. Sebelius (2012). The Affordable Care Act threatened to cut off all existing Medicaid funding, roughly 10% of a typical state’s budget, from any state that refused to expand Medicaid to new populations. The Court held that this crossed from incentive into coercion, calling it “economic dragooning that leaves the States with no real option but to acquiesce.”10Justia U.S. Supreme Court Center. National Federation of Independent Business v. Sebelius Congress can offer new money with new conditions. It cannot use existing funding for an unrelated program as a lever.
Where the exact tipping point sits between those two cases is unresolved.11Congress.gov. Anti-Coercion Requirement and Spending Clause Half a percent of a state budget was fine; 10% was too much. Anything in between has not been tested.
What the Tenth Amendment Does Not Do
The reservation of power to the states does not make state law immune from federal law. Article VI declares federal law “the supreme Law of the Land” and binds state judges to it, “any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.”12Congress.gov. Constitution of the United States – Article VI When a state law genuinely conflicts with a valid federal statute passed within an enumerated power, the state law loses.
Preemption comes in several forms. Congress can preempt expressly, by writing into a statute that it intends to override state law. It can preempt by implication, by regulating a field so completely that no space is left for state rules, or by making compliance with both regimes impossible. The Tenth Amendment protects state authority in the space the Constitution has not already assigned to the federal government; it does not create a state veto over federal action inside that space.
States also face direct constitutional prohibitions independent of the Tenth Amendment. They cannot coin money, enter treaties, or impose tariffs on goods from other states. And through the Fourteenth Amendment, ratified in 1868, the Supreme Court has applied nearly all of the Bill of Rights against state governments as well as federal ones.13Congress.gov. Early Doctrine on Incorporation of the Bill of Rights Free speech, the right to bear arms, protection against unreasonable searches, the right to counsel, protection against cruel and unusual punishment: each of these now limits state power. A state’s police power to protect public health, for instance, cannot override free exercise of religion without meeting demanding constitutional standards.
Where the Fights Are Now
Two current disputes show the doctrine at work.
Immigration enforcement pits federal authority against state and local policies that limit cooperation with federal immigration agents. Cities and states argue that the anti-commandeering doctrine prevents the federal government from forcing local police to honor federal detainer requests. Courts have largely agreed that states cannot be compelled to hold people solely on federal request, though they have split on whether federal laws requiring information-sharing cross the commandeering line.
State marijuana laws produce a parallel standoff. Dozens of states permit medical or recreational marijuana, while federal law still classifies it as a controlled substance. The Supremacy Clause means federal law technically prevails, but the anti-commandeering doctrine means the federal government cannot force state officers to enforce the federal prohibition. The result is a substance that is legal under state law and illegal under federal law at the same time, with actual enforcement depending on federal priorities and resources.
These are not anomalies. They are the kind of ongoing negotiation between national power and state self-governance that the Tenth Amendment was written to produce, resolved case by case rather than settled once for all.