Federal laws do override state laws, but only when a valid federal law actually conflicts with a state one, and only within the boundaries the Constitution sets for federal power. The short answer to whether federal laws override state laws is yes in a direct clash, no across the many areas the Constitution leaves to the states, and “it depends” in the large middle ground where the two systems operate side by side. The tiebreaker lives in Article VI, but so do its limits.
The Supremacy Clause Sets the Basic Rule
Article VI, Clause 2 of the Constitution provides that the Constitution itself, federal laws made under its authority, and treaties of the United States are the supreme law of the land, and that judges in every state are bound by them regardless of anything in state constitutions or state laws to the contrary.1Cornell Law School. Article VI – U.S. Constitution When a legitimate federal law directly conflicts with a state law, the federal law controls and the state law is unenforceable to the extent of the conflict.
The catch is in the words “made in pursuance” of the Constitution. A federal statute claims supremacy only when Congress had constitutional authority to pass it in the first place. If Congress acts outside its enumerated powers, the statute is not supreme, and the state law it purported to override stays in force. So the question is never simply “which law is federal?” It is whether Congress had the power to legislate on the subject at all, and whether the two laws actually collide.
The Three Ways Federal Law Displaces State Law
Courts call the mechanism preemption. Not every overlap between federal and state law triggers it. The analysis usually falls into three buckets.
Express Preemption
Sometimes Congress says so directly. A federal statute may contain language explicitly stating that it replaces state laws on the same subject. The Employee Retirement Income Security Act is one of the broadest examples: it provides that its provisions supersede any state laws to the extent they relate to any covered employee benefit plan.2Office of the Law Revision Counsel. 29 USC 1144 – Other Laws When Congress writes an express preemption clause, the court’s job is to interpret how far that language reaches.
Conflict Preemption
Even without explicit language, a state law falls if complying with both requirements is physically impossible, or if the state law stands as an obstacle to accomplishing what Congress set out to do. If a federal regulation requires a specific warning label on a product and a state law bans that same label, you literally cannot follow both. The state law gives way.
Field Preemption
In some areas the federal government has regulated so thoroughly that Congress clearly intended to occupy the entire field, leaving no room for state laws even if they don’t directly contradict federal rules. Immigration is the textbook example. When Arizona passed a law creating state penalties for immigration violations, the Supreme Court struck down most of the statute, holding that federal immigration law left no room for states to impose their own registration requirements or criminal penalties in that space.3Justia Law. Arizona v. United States, 567 U.S. 387 (2012)
What the Constitution Leaves to the States
Federal supremacy stops where federal power stops. The Tenth Amendment provides that powers not delegated to the federal government by the Constitution, and not prohibited to the states, are reserved to the states or to the people.4Cornell Law School. Tenth Amendment, U.S. Constitution This is the foundation for what are often called police powers, which give states authority to regulate the health, safety, and welfare of their residents.
Under these reserved powers, states control enormous swaths of everyday law. Family law, including marriage and divorce, is almost entirely a state matter. The same goes for most criminal law, property law, contract law, and professional licensing. When you get a driver’s license, register a business, or hire a licensed contractor, you are dealing with state-level authority. The federal government cannot legislate in these areas unless it can connect the regulation to one of its enumerated powers, such as the power to regulate interstate commerce.
What the Federal Government Cannot Force States to Do
Even where federal law is supreme, one line the federal government cannot cross is ordering state governments to carry out federal programs. This restriction, called the anti-commandeering doctrine, comes from the Tenth Amendment and the Constitution’s structure of dual sovereignty.
The Supreme Court articulated the principle in New York v. United States (1992), striking down a federal law that forced states to either regulate radioactive waste according to federal instructions or take ownership of the waste themselves. The Court held that Congress cannot commandeer state legislative processes by ordering states to enact or administer a federal regulatory program. Five years later, in Printz v. United States, the Court extended the rule to state executive officers, invalidating a provision of the Brady Act that required local law enforcement to conduct background checks on handgun buyers.5Cornell Law School. Printz v. United States The federal government could not conscript state officers to carry out a federal task.
The doctrine got its most dramatic recent application in Murphy v. NCAA (2018), where the Court struck down a federal law that prohibited states from authorizing sports gambling. The government argued that preventing a state from passing a law was different from forcing a state to pass one. The Court rejected that distinction as empty, holding that Congress cannot issue direct orders to state legislatures in either direction.6Supreme Court of the United States. Murphy v. National Collegiate Athletic Association
Anti-commandeering does not stop the federal government from enforcing its own laws directly. Federal agents can still enforce federal statutes in any state. What the doctrine prevents is Washington drafting state employees, state agencies, or state legislatures to do the enforcing for it.
Federal Money as a Workaround
When the federal government cannot command states directly, it often reaches the same result by attaching conditions to federal funding. Under the Spending Clause of Article I, Congress can offer states money in exchange for adopting particular policies. States can refuse and ignore the conditions. Few do.
The national minimum drinking age is the classic example. Congress did not mandate a drinking age of 21, which would likely violate anti-commandeering. Instead, it directed the Secretary of Transportation to withhold 8 percent of federal highway funds from any state that allows people under 21 to purchase or publicly possess alcohol.7Office of the Law Revision Counsel. 23 USC 158 – National Minimum Drinking Age Every state eventually raised its drinking age. The Supreme Court upheld the approach in South Dakota v. Dole (1987), establishing that conditional funding is permissible as long as the conditions are unambiguous, related to a federal interest, and do not amount to coercion.
That last piece has teeth. In NFIB v. Sebelius (2012), the Court held that the Affordable Care Act’s threat to strip all existing Medicaid funding from states that refused to expand the program was unconstitutionally coercive, because it put a gun to the states’ heads rather than offering a genuine choice. The line between permissible incentive and impermissible coercion is not always obvious, but the principle is clear: the federal government can offer carrots, not wield clubs.
When Both Laws Stand Together
Many areas are not exclusively federal or exclusively state. Both levels can levy taxes, run courts, and pass laws regulating workplaces or the environment. Whether the federal law “overrides” the state law in these zones depends on whether the two actually conflict.
Minimum Wage: A Floor, Not a Ceiling
The federal minimum wage under the Fair Labor Standards Act is $7.25 per hour, a rate that has not changed since 2009.8U.S. Department of Labor. State Minimum Wage Laws More than 30 states and the District of Columbia have set their own minimum wages above that floor, with rates reaching as high as $17.50 per hour in some jurisdictions. There is no conflict here because the federal law sets a floor, not a ceiling. Employers in states with higher minimums must pay the higher state rate. The federal law prevents any state from going below $7.25, and states are free to require more.
Marijuana: A Genuine Conflict
Marijuana is the most visible example of federal and state law pointing in opposite directions. Federal law still classifies marijuana as a Schedule I controlled substance, meaning it is treated as having no accepted medical use and a high potential for abuse.9Office of the Law Revision Counsel. 21 USC 812 – Schedules of Controlled Substances A majority of states have legalized it for medical use, recreational use, or both.
The federal government proposed rescheduling marijuana to Schedule III in May 2024, which would recognize accepted medical uses and lower abuse potential. That process is still pending. A December 2025 executive order directed the Attorney General to complete the rescheduling rulemaking as quickly as possible, but as of early 2026, the administrative hearing process has not concluded and marijuana remains Schedule I under federal law.10The White House. Increasing Medical Marijuana and Cannabidiol Research
Under the Supremacy Clause, federal law technically prevails, and someone operating a state-licensed dispensary could theoretically face federal prosecution. In practice, the federal government has largely declined to pursue individuals complying with state marijuana laws, but that enforcement discretion can change with any new administration. Compliance with state law is not a legal defense to a federal charge. Anyone operating in this space is navigating a genuine conflict between two levels of government.
Who Decides When Laws Collide
When federal and state laws collide, the federal judiciary serves as the referee. That power traces to Marbury v. Madison (1803), where the Supreme Court established that it is “emphatically the duty of the Judicial Department to say what the law is” and that when two laws conflict, courts must decide which one governs.11Justia Law. Marbury v. Madison, 5 U.S. 137 (1803) Federal courts at every level handle preemption challenges, and the Supreme Court has the final word. Its appellate jurisdiction includes the authority to review state court decisions that interpret federal law.12Cornell Law Institute. U.S. Constitution Annotated Article III Section 2 Clause 2 – Section: Supreme Court Review of State Court Decisions
Getting into court in the first place can be its own obstacle. The Eleventh Amendment and the broader doctrine of sovereign immunity generally bar private individuals from suing a state government without its consent, whether by its own citizens or by residents of other states.13Legal Information Institute (LII) / Cornell Law School. General Scope of State Sovereign Immunity Congress can override this immunity in limited circumstances when enforcing the Fourteenth Amendment, but the default rule is that suing a state is much harder than suing a private party. Even when a state law appears to violate federal law, getting a court to hear the challenge is not automatic.