State laws cannot override federal laws. Under the Supremacy Clause of the U.S. Constitution, when a state law genuinely conflicts with a valid federal law, the federal law wins and the state law gives way. But the question of whether state laws can override federal laws is more interesting than that flat answer suggests, because federal supremacy only reaches as far as the powers the Constitution actually gives the federal government. Outside those powers, states govern freely. And even inside them, Congress cannot force state officials to enforce federal programs. That is why state-legal marijuana dispensaries operate while marijuana remains a federal crime, and why states can set a minimum wage well above the federal one without breaking any rule.
What the Supremacy Clause Actually Says
Article VI, Clause 2 of the Constitution declares that the Constitution, federal laws made under it, and treaties are “the supreme Law of the Land,” and that judges in every state are bound by them regardless of anything in state law to the contrary.1Legal Information Institute. Article VI U.S. Constitution The framers added this because the Articles of Confederation had no equivalent, and states had routinely ignored national statutes.
Two limits are built into the clause itself. It only operates when a federal law actually conflicts with a state law, and it only reaches areas where the Constitution grants the federal government authority in the first place. A federal statute passed outside those enumerated powers has no supremacy to claim.
How Federal Law Displaces State Law: Preemption
Preemption is the tool courts use to decide whether a specific federal law knocks out a specific state law. The core question is always what Congress intended: to be the sole regulator in this area, or to leave room for states to add rules of their own.
Express Preemption
Sometimes Congress writes its intent directly into the statute. The Employee Retirement Income Security Act, for example, expressly supersedes “any and all State laws insofar as they may now or hereafter relate to any employee benefit plan.”2Office of the Law Revision Counsel. 29 USC 1144 – Other Laws When language like that is on the page, the analysis is relatively straightforward.
Field Preemption
When Congress does not spell out preemption, courts sometimes find it implied. Field preemption applies where the federal government has regulated an area so thoroughly that it occupies the whole field. In Arizona v. United States, the Supreme Court struck down a state law making it a crime for immigrants to fail to carry federal registration documents, holding that the federal registration scheme left no room for parallel state rules.3Justia. Arizona v United States 567 US 387 2012
Conflict Preemption
Conflict preemption applies when it is physically impossible to comply with both laws, or when the state law stands as an obstacle to what Congress was trying to accomplish. This is the most common route to preemption, and it is fact-heavy: the same state law might survive against one federal statute and fall against another.
What States Still Control
The Tenth Amendment reserves to the states every power the Constitution does not give the federal government or forbid to the states.4Legal Information Institute. Tenth Amendment That reserved authority is huge. Traffic law, family law, most criminal offenses, public education, zoning, professional licensing, and the general power to protect health, safety, and welfare all sit primarily with the states.
These powers are not unlimited. A state law that violates the Constitution or genuinely conflicts with valid federal law will still fall. But within their sphere, states are not junior partners of the federal government; they are separate sovereigns.
Why Congress Cannot Draft States Into Federal Enforcement
One consequence of that separation is the anti-commandeering doctrine. Even where a federal law is valid and supreme, Congress cannot order state legislatures to pass laws or order state officials to enforce federal programs.
The Supreme Court laid this down in New York v. United States, striking a federal law that effectively required states to legislate on radioactive waste disposal, and reinforced it in Printz v. United States, invalidating a portion of the Brady Handgun Act that required local sheriffs to conduct federal background checks. The federal government, the Court wrote, “may neither issue directives requiring the States to address particular problems, nor command the States’ officers… to administer or enforce a federal regulatory program.”5Legal Information Institute. Printz v United States In 2018’s Murphy v. NCAA, the Court applied the same doctrine to a federal statute that prohibited states from authorizing sports gambling, making clear that Congress may not tell state legislatures what to do or what not to do.
This is why so-called sanctuary jurisdictions can exist. Federal law bars state and local governments from restricting the sharing of immigration status information with federal authorities.6Office of the Law Revision Counsel. 8 USC 1373 – Communication Between Government Agencies and the Immigration and Naturalization Service But the federal government cannot require state or local police to actively enforce federal immigration law, honor immigration detainers, or dedicate their own budgets and personnel to federal operations.
When a Stricter State Law Is Not a Conflict
Plenty of state laws look like they override federal law but do not, because Congress wrote the federal statute as a floor rather than a ceiling. The minimum wage is the cleanest example. The federal minimum has been $7.25 an hour since 2009.7U.S. Department of Labor. Wages and the Fair Labor Standards Act The Fair Labor Standards Act says that when a worker is covered by both state and federal minimums, the higher rate applies. Roughly 30 states and the District of Columbia have set minimums above $7.25, with the top rates approaching $18 an hour.
No preemption problem arises because no one is being asked to violate federal law. An employer paying $16 an hour is also, automatically, paying more than $7.25. The same structure appears in environmental standards, employee leave, and consumer protection: states can add on top of federal minimums as long as the state law does not undo what Congress required. A state cannot cut below the federal floor, but it can build above it.
Marijuana: The Conflict That Has Not Been Resolved
The starkest ongoing collision between state and federal law is marijuana. The federal Controlled Substances Act classifies marijuana as a Schedule I substance, alongside heroin and LSD, making production, distribution, and possession federal crimes.8Office of the Law Revision Counsel. 21 USC 812 – Schedules of Controlled Substances A majority of states have legalized marijuana in some form. The Supreme Court in Gonzales v. Raich held that Congress’s Commerce Clause power reaches even local, state-legal marijuana activity, and that state legalization does not strip Congress of authority to regulate the drug nationally.9Justia. Gonzales v Raich 545 US 1 2005 In legal terms, federal law controls.
So why do state-legal dispensaries operate openly? The answer is prosecutorial discretion and appropriations, not a change in the underlying law. Since 2014, annual federal spending bills have included a rider (originally the Rohrabacher-Farr amendment) that bars the Department of Justice from using funds to interfere with state medical marijuana programs. That rider must be renewed each budget cycle. The Obama-era Cole Memo, which deprioritized enforcement against compliant state-legal operations, was rescinded in 2018 and has not been formally replaced.
In May 2024 the Department of Justice proposed rescheduling marijuana from Schedule I to Schedule III. As of late 2025 the proposal was awaiting an administrative law hearing, and in December 2025 an executive order directed the Attorney General to complete rescheduling as expeditiously as possible.10The White House. Increasing Medical Marijuana and Cannabidiol Research Rescheduling would not legalize marijuana federally, but it would reduce a good deal of the practical friction.
What the Conflict Costs the People Caught In It
Even where a state has fully legalized an activity, federal law continues to apply to anyone the federal government chooses to reach. Marijuana is the clearest illustration, but the pattern generalizes.
Firearms
Federal law prohibits anyone who is “an unlawful user of or addicted to any controlled substance” from possessing firearms or ammunition.11Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts Because marijuana remains a federal controlled substance, using it in a state where it is legal still makes you a prohibited person for federal firearms purposes. ATF Form 4473, which every buyer completes at a licensed dealer, asks the question directly, and answering it dishonestly is a federal felony.12ATF. Identify Prohibited Persons
Federally Assisted Housing
HUD has said that marijuana use, even under state law, is grounds for denial of admission to or eviction from federally assisted housing. Owners of HUD-assisted properties must deny admission to any household with a member using a federally controlled substance and must include lease terms allowing termination for such use.13U.S. Department of Housing and Urban Development. Use of Marijuana in Multifamily Assisted Properties Owners retain some discretion with existing tenants, but they cannot adopt policies that affirmatively permit use.
Federal Jobs and Security Clearances
Federal hiring and clearance decisions apply federal law. The FBI requires applicants to have been marijuana-free for at least three years; the CIA requires at least twelve months. Some U.S. Attorney offices have rejected applicants for admitting a single past use. A state medical card offers no protection, and disclosure on a clearance application can be disqualifying regardless of where the use occurred.
Business Taxes and Banking
Section 280E of the Internal Revenue Code denies deductions and credits to any business trafficking in Schedule I or Schedule II substances.14Office of the Law Revision Counsel. 26 USC 280E – Expenditures in Connection With the Illegal Sale of Drugs A state-legal dispensary cannot deduct rent, payroll, or other ordinary expenses on its federal return, producing effective tax rates that can exceed 70 percent. Banks face parallel exposure: serving a marijuana business risks federal money-laundering liability, which is why many financial institutions simply refuse the accounts.
Asset Forfeiture
Federal civil forfeiture reaches property connected to federal crimes. The government must show by a preponderance of the evidence that the property is subject to forfeiture and that a substantial connection existed between it and the offense.15Forfeiture.gov. 18 US Code 983 – General Rules for Civil Forfeiture Proceedings Cash, real estate, and equipment tied to state-legal marijuana activity are technically forfeitable, and the “innocent owner” defense does not extend to property that is illegal to possess under federal law.
How Courts Settle These Disputes
Preemption disputes are litigated in both state and federal courts, and the U.S. Supreme Court has the final word. Analysis always starts with what Congress intended. The outcomes are rarely all-or-nothing: in Arizona v. United States, the Court struck down three provisions of the state’s immigration law as preempted but allowed a fourth to stand pending real-world implementation.3Justia. Arizona v United States 567 US 387 2012 A single statute can be partly preempted and partly valid.
Businesses and individuals who are uncertain which law governs sometimes seek a declaratory judgment, a court ruling that clarifies rights and obligations before anyone is arrested, fined, or sued. The court does not award damages; it declares which law controls, and the parties adjust accordingly.
The structural picture is worth holding onto. Federal law sits at the top of the hierarchy, but only within the powers the Constitution grants. Outside those powers, states govern. Within them, states can still add stricter protections as long as they do not undo the federal rule, and even where federal law is supreme, Congress cannot draft state officials into enforcing it. Federal supremacy is real, and it is narrower than the phrase makes it sound.