If you are asking what is the supreme law of the land, the answer is the U.S. Constitution. The Supremacy Clause in Article VI, Clause 2 makes this rule plain. Under it, the Constitution, federal laws made under it, and U.S. treaties all rank above any state law. In addition, the clause tells every state judge to follow federal law when the two clash. This idea shapes daily life, from food labels to airline rules. It also shows up on the U.S. citizenship civics test. Below, you will learn what the clause says, what counts as supreme law, how preemption works, and where federal power stops. You will also see the key Supreme Court cases and a side-by-side look at federal and state law.
| Quick Fact | Answer |
|---|---|
| Supreme law | The U.S. Constitution |
| Source clause | Supremacy Clause, Article VI, Clause 2 |
| Includes | The Constitution, federal laws made under it, and U.S. treaties |
| Who enforces | Federal and state courts, with the U.S. Supreme Court as final judge |
| Key cases | Marbury v. Madison (1803), McCulloch v. Maryland (1819), Gibbons v. Ogden (1824), Cooper v. Aaron (1958) |
| Civics test answer | “The Constitution” (also “U.S. Constitution”) |
What Does “Supreme Law of the Land” Mean?
The phrase means the Constitution sits at the top of all American law. No state law, state constitution, or local rule can override it. The words come straight from the Supremacy Clause, which reads:
“This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.”
In plain words, the clause does two jobs. First, it names three types of supreme law. Second, it orders state judges to apply federal law even when their own state says something different. The Library of Congress explains the clause’s history in its Article VI annotation.
What Counts as Supreme Law and the Legal Hierarchy
Three things count as supreme law: the Constitution, valid federal statutes, and treaties. However, they do not stand as equals. The Constitution beats everything else, and federal law beats state law.
Here is the basic order, from highest to lowest:
- U.S. Constitution: the top rule. Every other law must fit within it.
- Federal statutes and treaties: laws Congress passes and treaties the Senate approves. Courts generally treat them as equal, so a later one can win over an earlier one.
- Federal regulations: rules that agencies write under power Congress gives them.
- State constitutions: the top law inside each state.
- State statutes and regulations: laws from state legislatures and agencies.
- Local laws: city and county ordinances.
Both levels also split into civil and criminal rules. If you want that background, see our guide on civil vs. criminal law.
How Federal Preemption Works
Preemption means a valid federal law wins and the conflicting state law stops working. Courts recognize three main kinds: express, field, and conflict preemption.
- Express preemption: Congress says it outright in the law. For example, a statute may state that no state can add its own rules on a topic.
- Field preemption: Congress covers a subject so fully that it leaves no room for states. Courts have treated immigration registration and nuclear safety this way.
- Conflict preemption: a person cannot obey both laws at once, or the state law blocks what Congress wanted to do. In that case, the federal rule wins.
Still, preemption is not automatic. Courts usually assume Congress did not mean to displace traditional state powers, such as health and safety.
Limits on the Supreme Law of the Land
Federal law is supreme only when it is constitutional. Congress must act within its listed powers, and it cannot order states to carry out federal programs.
The clause itself sets the first limit. It covers federal laws made “in Pursuance” of the Constitution. Therefore, a law Congress had no power to pass gets no supremacy at all. Next, the Tenth Amendment reserves to the states, or the people, all powers the Constitution does not give the national government.
From these ideas, the Supreme Court built the anti-commandeering rule. In Printz v. United States (1997), the Court struck down a part of the Brady Act that required local sheriffs to run background checks on gun buyers. Later, in Murphy v. NCAA (2018), the Court struck down a federal law that barred states from authorizing sports betting. In both cases, the Court said Congress can regulate people directly, but it cannot command state governments.
Key Supreme Court Cases
Four early and mid-era cases built the modern meaning of federal supremacy. Together, they let courts strike down laws and keep states from defying federal power.
- Marbury v. Madison (1803): Chief Justice John Marshall declared that courts can strike down laws that conflict with the Constitution. This power is called judicial review.
- McCulloch v. Maryland (1819): The Court held that Congress could create a national bank and that Maryland could not tax it.
- Gibbons v. Ogden (1824): The Court struck down a New York steamboat monopoly because it clashed with a federal coasting license. The case gave Congress broad power over interstate commerce.
- Cooper v. Aaron (1958): Arkansas officials tried to delay school integration in Little Rock. All nine justices ruled that states must follow the Court’s decision in Brown v. Board of Education and cannot nullify it.
State Constitutions and Preemption in Daily Life
Each state constitution is the highest law within that state, but it still ranks below federal law. States keep wide power over areas the Constitution leaves to them.
For instance, states write most rules on marriage, divorce, property, and contracts. Some states recognize common law marriage, while most do not. Likewise, state constitutions can give people more rights than the federal one, but never fewer.
You meet preemption more often than you might think:
- Food labels: Federal law sets the format of the Nutrition Facts panel, so states cannot demand a different version.
- Airlines: Federal law blocks states from regulating airline prices, routes, and services.
- Minimum wage: The federal minimum is a floor. States can set a higher wage because paying more does not conflict with federal law.
- Immigration: In Arizona v. United States (2012), the Court struck down several parts of an Arizona immigration law as preempted.
Why “What Is the Supreme Law of the Land” Is a Civics Test Question
USCIS asks it because the Constitution is the base of the whole U.S. government. The correct answer is simply “the Constitution.”
On the 2008 civics test, it was question 1. On the 2025 civics test, which USCIS began using for applications filed on or after October 20, 2025, it is question 2. The 2025 version marks it with an asterisk, which means applicants age 65 or older with 20 or more years as permanent residents may study it from a shorter list. Under the 2025 test, an officer asks up to 20 questions, and applicants must answer 12 correctly. You can find the official lists on the USCIS Study for the Test page.
Federal Law vs. State Law: A Comparison
| Feature | Federal Law | State Law |
|---|---|---|
| Top source | U.S. Constitution | State constitution |
| Who makes it | Congress, federal agencies, President and Senate (treaties) | State legislatures and agencies |
| Reach | Whole country | One state only |
| Rank in a conflict | Wins, if constitutional | Gives way to valid federal law |
| Power base | Only powers the Constitution lists | General police power over health, safety, and welfare |
| Typical topics | Immigration, currency, interstate trade, national defense | Marriage, family law, most crimes, property, contracts |
| Final interpreter | U.S. Supreme Court | State’s highest court (on state law) |
Conclusion
The U.S. Constitution is the supreme law of the land, and the Supremacy Clause in Article VI makes it so. Valid federal laws and treaties share that top status, and state judges must follow them. Even so, federal power has firm limits. Congress must act within the Constitution, and it cannot commandeer state officials. Meanwhile, states keep broad control over everyday matters like family and property law. For more plain-English guides, browse our Law category. This article gives general information, not legal advice.
Frequently Asked Questions
Is the Supreme Court the supreme law of the land?
No. The Constitution is the supreme law. The Supreme Court interprets it and has the final word on what it means.
Where in the Constitution is the Supremacy Clause?
You will find it in Article VI, Clause 2.
Can a state ignore a federal law it disagrees with?
No. In Cooper v. Aaron (1958), the Court rejected that idea. However, a state can challenge a federal law in court, and it can decline to help enforce federal programs under the anti-commandeering rule.
What should I say on the citizenship test?
Say “the Constitution” or “the U.S. Constitution.” USCIS accepts either answer.
Sources
- U.S. Constitution, Article VI, Clause 2 (Supremacy Clause) and Tenth Amendment
- Library of Congress, Constitution Annotated: Article VI, Clause 2
- U.S. Citizenship and Immigration Services, 2008 and 2025 Civics Test Questions
- Marbury v. Madison, 5 U.S. 137 (1803)
- McCulloch v. Maryland, 17 U.S. 316 (1819)
- Gibbons v. Ogden, 22 U.S. 1 (1824)
- Cooper v. Aaron, 358 U.S. 1 (1958)
- Printz v. United States, 521 U.S. 898 (1997)
- Arizona v. United States, 567 U.S. 387 (2012)
- Murphy v. National Collegiate Athletic Association, 584 U.S. 453 (2018)