Power in the United States is divided between the federal and state governments by a constitutional design that hands the national government a specific list of jobs, reserves everything else to the states, lets both levels share a handful of powers like taxation, and makes federal law supreme when the two collide. The Tenth Amendment draws the clearest line: anything the Constitution doesn’t grant to the federal government stays with the states or the people.1Legal Information Institute. Tenth Amendment The boundary has shifted since 1789 through Supreme Court rulings, the growth of interstate commerce, and the federal government’s use of funding conditions, but the basic architecture still governs who can do what.
What Only the Federal Government Can Do
Article I, Section 8 lists the specific powers Congress holds. These include coining money and regulating its value, regulating commerce with foreign nations and among the states, establishing post offices, declaring war, and raising armies.2Legal Information Institute. Section 8 Enumerated Powers The framers assigned these responsibilities to Washington because they require national uniformity. Letting each state coin its own currency or negotiate its own trade deals with foreign countries would have been chaotic even in the 1790s.
Beyond the explicit list, Congress exercises implied powers through the Necessary and Proper Clause, which authorizes any law needed to carry out its enumerated duties.2Legal Information Institute. Section 8 Enumerated Powers The Supreme Court established this principle in 1819 in McCulloch v. Maryland, holding that Congress could charter a national bank even though the Constitution never mentions banks. That reasoning opened the door for federal agencies, regulatory bodies, and programs that didn’t exist at the founding but serve enumerated purposes.
Federal law backs these powers with serious penalties. Counterfeiting U.S. currency, for example, carries up to 20 years in federal prison.3Office of the Law Revision Counsel. 18 USC 471 – Obligations or Securities of United States The federal government also administers the patent and copyright systems, granting inventors and authors temporary exclusive rights.
The Commerce Clause gives Congress power to regulate commerce “among the several States,” and the Supreme Court has interpreted that language broadly. In Wickard v. Filburn (1942), the Court held that even purely local activity can be regulated by Congress “if it exerts a substantial economic effect on interstate commerce.”4Justia. Wickard v. Filburn, 317 U.S. 111 (1942) That test gave Congress a constitutional basis for regulating workplace safety, environmental standards, civil rights in private businesses, and drug policy. The expansion isn’t unlimited. In United States v. Lopez (1995), the Court struck down a federal ban on guns near schools because the link to interstate commerce was too thin.
Immigration Belongs to Washington
The Constitution doesn’t mention immigration by name, but the Supreme Court has long treated it as exclusively federal. Courts point to Congress’s power over naturalization, its authority to regulate foreign commerce, and the idea that controlling entry into the country is inherent to national sovereignty.5Constitution Annotated. Overview of Congress’s Immigration Powers The Court has stated that immigration policymaking “is entrusted exclusively to Congress.” States can cooperate with federal enforcement, but they cannot run their own parallel immigration systems or override federal admission decisions.
What States Handle on Their Own
The Tenth Amendment states plainly: “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.”1Legal Information Institute. Tenth Amendment This creates a large zone of state authority, often called “police powers,” covering health, safety, welfare, and public morals within each state’s borders.
In practice, states run the systems that touch your daily life most directly:
- Education. States establish and fund public school systems, set curriculum standards, and license teachers.
- Professional licensing. Doctors, lawyers, engineers, contractors, and dozens of other professions need state-issued licenses. Each state sets its own requirements, which is why moving often means reapplying for your credentials.
- Family law. Marriage licenses, divorce, child custody, and adoption run through state courts, not federal agencies.
- Criminal law. The vast majority of violent and property crimes are prosecuted under state law by local district attorneys.
- Land use. Zoning ordinances, building codes, and property rules come from state and local government.
- Traffic and vehicles. Driver’s licenses, vehicle registration, and traffic laws are state responsibilities, with fees and rules varying widely.
The variation is real. Forming an LLC costs anywhere from $50 to over $500 depending on the state. Driver’s license fees range from under $15 to nearly $90. Those differences reflect independent fiscal and policy choices by each state, which is what the Tenth Amendment protects.
State police powers become especially visible during public health emergencies. States have broad authority to issue quarantine orders, mandate vaccinations, and restrict gatherings when public health demands it, an authority the Supreme Court upheld in 1905 in Jacobson v. Massachusetts.
What Both Levels Do at Once
Some powers aren’t exclusive to either level. Both federal and state governments exercise these “concurrent powers” simultaneously, and neither needs the other’s permission to act.
Taxation is the clearest example. The federal government collects income tax through IRS Form 1040,6Internal Revenue Service. About Form 1040, U.S. Individual Income Tax Return while states run separate tax systems. Eight states levy no individual income tax at all, while top rates in other states reach as high as 13.3%. Both levels borrow money by issuing bonds, Treasury bonds at the federal level and municipal bonds at the state and local level, to fund infrastructure and manage budgets.7Legal Information Institute. Borrowing Power
Court systems operate at both levels. Federal courts handle cases involving federal law, constitutional questions, and disputes between citizens of different states. State courts handle everything else, which in volume terms is the overwhelming majority of litigation in America. Law enforcement is similarly shared. Federal agents investigate drug trafficking rings and bank fraud while state and local police handle street crime, domestic violence, and traffic enforcement, and the two levels frequently cooperate through joint task forces.
Business regulation is another shared space. States charter corporations and LLCs through their secretaries of state, but once a company sells securities to public investors, the federal Securities and Exchange Commission steps in. A business operating in multiple states deals with both systems.
When Federal and State Law Conflict
Article VI declares that federal law is “the supreme law of the land,” and state judges are bound by it regardless of what their own state constitutions say.8Legal Information Institute. Article VI, U.S. Constitution When a valid federal law directly conflicts with a state law, the federal law wins.
Federal preemption takes several forms. Sometimes Congress explicitly states that federal law overrides state regulation on a topic. Other times, federal regulation is so comprehensive that courts conclude Congress meant to occupy the entire field. And when a state law makes compliance with both state and federal requirements impossible, the state law gives way.
Marijuana Shows the Tension
Federal law classifies marijuana as a Schedule I controlled substance, the most restrictive category, alongside heroin and LSD.9Office of the Law Revision Counsel. 21 USC 812 – Schedules of Controlled Substances Yet as of 2026, 25 states have legalized recreational marijuana and 39 allow medical use. Under the Supremacy Clause, federal law technically prevails, and the federal government could prosecute marijuana businesses even in states where they’re fully licensed.
In practice, the federal government has largely chosen not to enforce marijuana laws in states with robust regulatory systems, relying on prosecutorial discretion. State-legal businesses still can’t access federal banking services, can’t deduct normal business expenses on their federal taxes, and face theoretical criminal liability for conduct their state permits. Until Congress either legalizes marijuana federally or explicitly authorizes state programs, the conflict remains unresolved.
You Can Be Prosecuted Twice for the Same Act
Because federal and state governments are separate sovereigns with independent sources of authority, both can prosecute the same person for the same conduct without violating the Fifth Amendment’s protection against double jeopardy. The Supreme Court affirmed this in Gamble v. United States (2019), holding that when a single act breaks both federal and state law, it constitutes two distinct offenses, one against each sovereign.10Justia. Gamble v. United States, 587 U.S. ___ (2019)
Overlapping jurisdiction is common for drug offenses, firearms charges, carjacking, and a growing list of crimes Congress has federalized. A person convicted of possessing a firearm as a felon under state law can face a second federal prosecution for the same conduct under federal firearms statutes. Federal mandatory minimums often exceed state penalties, giving federal prosecutors significant leverage.
How Federal Money Shapes State Policy
The Constitution’s Spending Clause gives Congress power to tax and spend for the “general welfare,” and Congress uses this authority to shape state policy in areas where it might lack direct regulatory power. The mechanism is straightforward: Congress offers states money with conditions attached, and states that want the funding must comply.
The Supreme Court blessed this approach in South Dakota v. Dole (1987), upholding a federal law that withheld 5% of highway funding from states allowing anyone under 21 to purchase alcohol.11Justia. South Dakota v. Dole, 483 U.S. 203 (1987) The Court held that spending conditions must relate to the purpose of the federal program and cannot be so coercive that states have no real choice. Every state ultimately raised its drinking age to 21.
There are limits. In NFIB v. Sebelius (2012), the Court struck down the Affordable Care Act’s requirement that states expand Medicaid or lose all existing Medicaid funding. Seven justices agreed that threatening to pull funding equal to roughly 10% of a state’s entire budget crossed from encouragement into coercion.12Legal Information Institute. Anti-Coercion Requirement and the Spending Clause Congress can dangle new money with new conditions, but it can’t threaten to revoke massive existing funding streams as leverage for unrelated policy changes.
Federal grants come in two main forms. Categorical grants restrict spending to narrow purposes, so a WIC nutrition grant must fund nutrition services, not road repairs. Block grants give states more flexibility within broad program goals, which is why states set different eligibility rules for programs like Temporary Assistance for Needy Families even though federal dollars fund them.
What Neither Level Can Do
The Constitution doesn’t just distribute power, it restricts it. Article I, Section 9 limits the federal government, while Section 10 limits the states.13Legal Information Institute. Article I, U.S. Constitution Some prohibitions apply to both. Neither Congress nor any state legislature can pass a bill of attainder (a law declaring someone guilty without a trial) or an ex post facto law (a law criminalizing conduct retroactively). Neither can grant titles of nobility.
Other restrictions target only one level. States cannot enter into treaties with foreign nations, coin money, or go to war unless actually invaded.14Legal Information Institute. U.S. Constitution Annotated Article I Section 10 – Powers Denied States States can enter compacts with other states if Congress consents, an authority used to create multistate agreements on water rights and transportation.15Constitution Annotated. Overview of Compact Clause The federal government cannot tax goods exported from any state, a restriction found in Article I, Section 9.16Constitution Annotated. Export Clause and Taxes
How the Bill of Rights Reaches State Governments
The Bill of Rights originally restrained only the federal government. A state could theoretically have restricted speech or conducted unreasonable searches without violating the Constitution as written in 1791. That changed with the Fourteenth Amendment, ratified in 1868, which declares that no state shall “deprive any person of life, liberty, or property, without due process of law.”17Legal Information Institute. 14th Amendment, U.S. Constitution
Through selective incorporation, the Supreme Court has used that Due Process Clause to apply nearly all of the Bill of Rights to state governments one provision at a time. Freedom of speech, the right to bear arms, protection against unreasonable searches, the right to counsel in criminal cases, and most other Bill of Rights protections now limit state governments just as they limit the federal government. The process stretched across decades of case-by-case decisions, each asking whether a particular right is fundamental enough to qualify. Only a handful of provisions remain unincorporated, including the Third Amendment’s restriction on quartering soldiers and the Seventh Amendment’s civil jury trial guarantee.
The practical effect is large. When a state legislature passes a law restricting protest activity or a local police department conducts a search without a warrant, the constitutional challenge comes through the Fourteenth Amendment’s application of the Bill of Rights. Individual rights function as a floor beneath which no level of government can sink, whether the threat comes from Washington or a state capital.