Federalism limits the power of government by dividing authority between the national government and the states, then setting constitutional boundaries on both. Congress can only act on powers the Constitution lists. States keep everything else, but they cannot cross into areas the Constitution closes to them. Courts police the line. And because fifty states run their own governments alongside Washington, no single authority controls everything a person’s life touches.
The Federal Government Only Has the Powers Listed
Congress operates on a short leash. It can exercise only the powers the Constitution specifically grants, most of them in Article I, Section 8: regulating interstate commerce, declaring war, coining money, establishing post offices, raising military forces, and collecting taxes for the national defense and general welfare.1Congress.gov. Constitution Annotated – Article I Section 8 If a power isn’t on the list, Congress doesn’t have it.
The Tenth Amendment states that rule directly. Ratified in 1791, it provides that any powers not given to the federal government, and not denied to the states, belong to the states or the people.2Congress.gov. Tenth Amendment The default runs toward the states.
The Constitution also lets Congress pass laws “necessary and proper” for carrying out its enumerated powers, and that clause has generated more federalism fights than any other. In McCulloch v. Maryland (1819), Chief Justice John Marshall held that “necessary” doesn’t mean “absolutely essential”; it means “appropriate and legitimate,” covering methods that further an objective the Constitution already authorizes.3Justia. McCulloch v. Maryland Under that reasoning, Congress could charter a national bank because a bank was a practical tool for managing finances Congress was empowered to manage.
Marshall also drew the line. The means Congress picks must be plainly adapted to a legitimate constitutional end and cannot be otherwise prohibited by the Constitution. The Necessary and Proper Clause expands the toolkit. It does not expand the mission.
What the States Keep
The powers reserved to the states cover most of what people encounter in daily life. States create local governments, run public schools, operate their own court systems, and define and enforce most criminal law. The Supreme Court has described the suppression of violent crime as perhaps the clearest example of the police power the framers denied to the national government and left with the states.4Congress.gov. Overview of Tenth Amendment, Rights Reserved to the States and the People
States also regulate business conducted entirely within their borders, license professions, manage public health and safety, and set their own tax policies. Each state has its own constitution and its own legislative, executive, and judicial branches. That produces fifty independent power centers the federal government has to work around instead of command.
Some powers overlap. Federal and state governments can both levy taxes, establish courts, borrow money, and spend for the general welfare. Neither level holds a monopoly even where both can act.
Limits the Constitution Places on States
Federalism doesn’t only restrain Washington. The Constitution also fences in the states, keeping them from undermining national unity or reaching into federal territory.
Direct Prohibitions
Article I, Section 10 bars states outright from entering treaties or alliances, coining their own money, granting titles of nobility, or passing laws that retroactively punish conduct or impair existing contracts. Other actions need congressional consent, including imposing duties on imports or exports, keeping military forces during peacetime, and entering agreements with other states or foreign powers.5Congress.gov. Section 10 – Powers Denied States
The Supremacy Clause and Preemption
Article VI declares that the Constitution, federal statutes made under it, and U.S. treaties are “the supreme Law of the Land,” binding on every state judge no matter what a state constitution or state law says.6Constitution Annotated. Article VI – Supreme Law, Clause 2 When valid federal law conflicts with state law, the federal law wins.
Congress sometimes preempts state regulation completely in a field. Other times it sets a federal floor and lets states go stricter. When a law doesn’t clearly address preemption, the Supreme Court prefers readings that avoid displacing state law, reflecting the presumption that states keep their authority unless Congress clearly takes it away.
The Dormant Commerce Clause
Even when Congress hasn’t acted, the Constitution’s grant of commerce power to the federal government implies a restriction on states. Courts call this the “dormant” Commerce Clause: states cannot pass laws that discriminate against interstate commerce or impose burdens on it that outweigh the state’s legitimate interest in regulating local matters. States have real room to regulate inside their borders, but they can’t use that authority to favor local businesses over out-of-state competitors or to break up the national market.
Congress Cannot Order States Around
One of the most practical checks federalism places on Washington is the rule that Congress cannot force state governments to act as its agents. The Supreme Court calls this the anti-commandeering doctrine. Congress can regulate individuals directly. It cannot conscript state officials to carry out federal programs.
The doctrine took shape in New York v. United States (1992), where the Court struck down a federal law that effectively required state legislatures to enact specific waste disposal rules. Congress cannot commandeer state legislative processes by ordering states to pass particular laws.7Legal Information Institute. Anti-Commandeering Doctrine Five years later, in Printz v. United States (1997), the Court extended the rule to state executive officials. Congress had required local law enforcement officers to run background checks on handgun purchasers under the Brady Act, and the Court found this “fundamentally incompatible” with dual sovereignty. Officers could volunteer. Congress could not order them.
In Murphy v. NCAA (2018), the Court went further, holding that Congress cannot even prohibit states from passing certain laws. A federal statute barring states from authorizing sports gambling violated the same principle: “Congress cannot issue direct orders to state legislatures,” whether the order demands action or forbids it.8Supreme Court of the United States. Murphy v. National Collegiate Athletic Association The rule also serves accountability. When the federal government has to enforce its own laws instead of pushing that work onto states, voters can see which level of government is responsible for what.
Money Comes With Limits Too
What Congress can’t mandate outright, it often pursues through funding. The federal government sends hundreds of billions of dollars to states each year for highways, education, healthcare, and other programs, and it routinely attaches conditions. The Supreme Court approved this approach in South Dakota v. Dole (1987), which upheld Congress’s decision to withhold a portion of federal highway funds from states that allowed people under 21 to buy alcohol.9Justia. South Dakota v. Dole Conditional spending is permitted so long as it promotes the general welfare, the conditions are clear, they relate to a federal interest in the program, and they aren’t independently unconstitutional.
The spending power has a breaking point, though. In National Federation of Independent Business v. Sebelius (2012), the Court ruled that Congress crossed from persuasion into coercion when the Affordable Care Act threatened to strip all existing Medicaid funding from states that refused to expand the program. For many states, that funding ran higher than a fifth of total expenditures. “When pressure turns into compulsion,” the condition violates federalism.10Justia. National Federation of Independent Business v. Sebelius Congress can offer carrots. It cannot hold a state’s existing budget hostage to force new compliance.
Courts Enforce the Boundaries
Federal courts referee these disputes, and judicial review is the strongest tool they hold: the power to strike down laws that exceed constitutional authority.
United States v. Lopez (1995) is a landmark example. The Gun-Free School Zones Act of 1990 made it a federal crime to possess a firearm near a school. The Supreme Court struck it down, holding that possessing a gun in a local school zone is not an economic activity with a substantial effect on interstate commerce, so Congress could not regulate it under the Commerce Clause.11Legal Information Institute. United States v. Lopez It was the first time in roughly sixty years that the Court had invalidated a federal law for exceeding Commerce Clause authority. Congress then rewrote the statute to require that the firearm “has moved in or that otherwise affects interstate or foreign commerce,” tying the prohibition to an enumerated power.12Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts The Court set a boundary and Congress adjusted.
Fifty States, Fifty Experiments
Beyond the formal doctrines, federalism limits power simply by allowing fifty states to try different approaches to the same problem. Justice Louis Brandeis captured this in his 1932 dissent in New State Ice Co. v. Liebmann, writing that “a single courageous state may, if its citizens choose, serve as a laboratory; and try novel social and economic experiments without risk to the rest of the country.”
That’s a structural barrier to centralization. When states design their own healthcare programs, environmental rules, criminal justice reforms, and education systems, the federal government isn’t the sole source of policy. States that get something right invite imitation. States that get it wrong provide a warning. Citizens who disagree with their state’s approach can push for change locally or move somewhere whose policies fit them better. That competitive dynamic keeps power distributed in a way no single constitutional clause could accomplish on its own.