(This is an attempt at a canonical question about an important distinction in US law and politics that is different than many other countries. It was suggested by this comment on another question. I'm looking for a "101-level primer" not a "law-review deep dive".)

In the US, is there a clear division of responsibility between the kinds of laws that are passed by the US Congress, compared to the laws that are passed by state legislatures? (Or even smaller jurisdictions like county boards and city councils, for that matter?)

Is this a widely understood and agreed-upon question? Or is it controversial?

If state and federal law appear to contradict each other, how is that resolved?

If a state law and a federal law create different (but not contradictory) regulations about something, how do they interact? For example, if my state's minimum wage is $9.50/hr but the federal minimum wage is $7.25/hr, what is my effective minimum wage?

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    Are we looking for what is the codified relationship between the two, the actual relationship between the two, or some blended third option? Commented Nov 20, 2017 at 21:24
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    @DrunkCynic I'm mostly looking for a 101-level primer on how it works in practice, not a law-review deep-dive into Federalism and history of legal precedents. Something we can link people to when they ask "why isn't (x) a law in the US?" I'll try to simply the question a bit to make it more clear.
    – BradC
    Commented Nov 20, 2017 at 21:27
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    Without careful scoping this question will get very broad, and very controversial, quickly. The powers of the Federal Government are enumerated in the Constitution, but many of those clauses have been debated extensively without resolution: interstate commerce, general welfare, etc. Commented Nov 20, 2017 at 21:32
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    "is there a typical method for deciding" = the judicial branch
    – user1530
    Commented Nov 20, 2017 at 21:38
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    @DrunkCynic Edited to streamline and narrow, let me know what you think. "There is widespread disagreement" should probably be part of a good answer, even if those disagreements aren't fully explored.
    – BradC
    Commented Nov 20, 2017 at 21:42

4 Answers 4


Division of Powers Between State and Federal Governments

There are some powers that are reserved solely to the federal government, some that can only be exercised locally or by the states, and yet others which can be (and are) exercised by all of the above.

Powers Reserved Solely to the National (Federal) Government

Several powers are reserved by the U.S. Constitution exclusively to the national government (commonly called the 'federal' government.)

  • Foreign relations, especially treaties
  • Coining money
  • Imposing duties on imports or exports
  • Keeping troops or ships of war during peace time
  • Engaging in war, unless actually invaded or in imminent danger

These limitations on state governments are laid out in Article I, Section 10 of the Constitution of the United States.

Powers Reserved to the State and Local Governments

The Tenth Amendment to the Constitution of the United States (the last of the ten amendments known as the Bill of Rights) says:

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.

So, in theory, any power that isn't explicitly granted by the U.S. Constitution to the federal government is reserved to the states and not available to the federal government. The exception is when a power is not granted to the federal government and is explicitly banned by the Constitution to the state governments, in which case neither may exercise that power. The latter would include cases such as granting titles of nobility or making ex post facto laws, for example, which is not possible for any level of government in the U.S.

In practice, however, this is more murky, as courts have occasionally allowed the federal government to exercise powers in all sorts of different things under incredibly broad interpretations of the Interstate Commerce Clause. This is why all sorts of federal laws and regulations will contain language similar to "when engaging in interstate commerce" or "for the purposes of engaging in interstate commerce," since the federal government technically has no Constitutional authority to regulate commerce within a state.

For example, even federal drug laws are deemed to be authorized under the Commerce Clause, as they regulate commerce of the drugs. Courts have further ruled in many cases that trade within a state may be regulated where it's deemed necessary to regulate interstate trade.

Powers Exercised at Both State and Federal Levels

There are many areas where federal powers overlap state and/or local powers. Drug laws are again an example of this, as are many criminal laws. So long as the two do not disagree, both are applicable and cases could be prosecuted under either. The lack of a federal law does not ban a state (or even a city or county) from making a law, though the federal government could explicitly make a law banning states from making a law restricting something.

For a more in-depth look at which government services are run and funded by which levels of government, see this answer on skeptics.SE.

What if State and Federal Law Conflict?

Article VI of the U.S. Constitution states that:

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, anything in the Constitution or laws of any State to the contrary notwithstanding.

So, if state and federal law disagree on a matter where the federal government has power to make that law, the federal law wins.

Again, however, what happens in practice can be different. In the particular example of laws regarding marijuana, there is a federal law banning its possession or sale in most cases, but some states do not impose a state law against it. In these cases, state and local law enforcement normally would not make arrests on these crimes. Federal law enforcement still could, however, under the federal laws. But the executive branch of the federal government could decide (and, in this case, has decided) to not do this. Thus, it's still technically illegal in the entire U.S., but those laws are effectively not enforced in the states that have no law against it.

The federal government could, however, decide to resume enforcing these laws any time it wanted to and the states would have little-to-no recourse to stop it from doing so, other than attempting to argue in court that federal drug laws aren't authorized under the Constitution in the first place. This would be a difficult case for the state to win in the current legal environment of broad interpretations of the Commerce Clause.

Additionally, if a state law and a local law conflict, it is also usually the case that the state law will preempt the local one. Unlike the federal government, state governments are not constrained to the powers enumerated in the federal constitution. In general, the only way for a local law which contradicts a state law to stand in a challenge would be for the state law to be struck down, such as if it violated some provision of the federal constitution or of that state's constitution. Otherwise, the state law will preempt the local law.

Who decides if they really conflict?

If a state law or local law is thought to be in violation of a federal law or the federal Constitution, it can be challenged in court as such by someone who is deemed by the court to have standing to bring the case. The courts will then rule whether or not the state law violates the federal law and, if it does, the courts will strike down the state law. If the parties still disagree, they can appeal the decision to higher appeals courts, possibly all the way up to the U.S. Supreme Court. The Supreme Court has the final say in this, as described in Article III of the U.S. Constitution.

On the flip side, if the federal government creates a law that is thought to exceed its enumerated powers, someone with standing can challenge it in court. If the courts rule the federal law exceeds the power of the federal government, the federal law will be struck down. Again, one or more states could potentially themselves be the party with standing to bring the suit here. And again, rulings can be appealed through appellate courts, potentially up to the U.S. Supreme Court, which would have the final say as per Article III.

Once the U.S. Supreme Court has ruled on a matter of U.S. Constitutional law, the only ways to change it are either for the Supreme Court to overturn their decision in a later ruling on a different case or for the U.S. Constitution to be amended, according to the process set out in Article V.

What if the State or Federal Law is More Restrictive than the Other?

If a state law is more restrictive than a federal law, but does not contradict the federal law, then the more restrictive state law applies (and the same goes for local laws.)

In the particular mentioned example of federal vs. state (vs. local) minimum wages, the most restrictive (highest) minimum wage in a given jurisdiction would apply. So, if the federal government has a $7.25/hr minimum wage, but the state government has as $10 minimum wage, the minimum legal wage in that state is $10. If a city in that state then decides to impose a $12 minimum wage, then the minimum wage inside that city is $12.

Is the Division of Powers Settled or Controversial?

Some parts are very unambiguous and settled (for example, no states are going to be coining money or declaring war any time soon,) but others remain quite controversial.

In general, those who follow an originalist philosophy of legal interpretation tend to view the legal role of the federal government in a more limited manner than those who do not. Conservatives and, especially, libertarians tend to favor originalism, while liberals tend to favor loose constructionism. As a result, conservatives and libertarians typically take a more narrow view of the legal powers of the federal government than do liberals.

The Commerce Clause

One of the largest points of contention is, as previously alluded to, the meaning of the Commerce Clause. Loose constructionists (mostly liberals) tend to view the powers granted to the federal government by the commerce clause much more broadly than do originalists (mostly conservatives and libertarians.)

A relatively recent example that highlights the disagreement in regards to the Commerce Clause was National Federation of Independent Business v. Sebelius (Wiki). In this case, the federal mandate for individuals to purchase health insurance or else pay a penalty was challenged in court. The Supreme Court's interpretation of the Commerce Clause here was divided 5-4.

Four justices (from the liberal wing of the court) held that the mandate to purchase insurance counted as a regulation of commerce under the Commerce Clause. However, the majority of the court (the 5 more conservative justices) rejected that interpretation, ruling that the Commerce Clause can't be used to force someone to unwillingly engage in commerce, but rather only to regulate existing commerce. Ultimately, however, a majority of the court upheld the penalty by ruling that it was a tax and, thus, authorized by the taxation clause.

This case also brings up an interesting example of the differences between federal powers and state powers. While, as the court ruled, the federal government has no power to force someone to engage in commerce, due to the lack of an enumerated constitutional power allowing it to do so, this limitation applies only to the federal government. On the other hand, nearly all, if not all, states already have laws requiring the purchase of automobile insurance and these laws are not set up as a tax. So, this is an example of a power that the state governments can wield, but not the federal government.

  • Comments are not for extended discussion; this conversation has been moved to chat. Commented Nov 23, 2017 at 21:40
  • A small part of this answer is incorrect. States are explicitly allowed to coin money (and there are several Supreme Court decisions which back this up); however they do not because the federal government can impose a tax on the usage of state coinage.
    – Viktor
    Commented Feb 14, 2018 at 0:41
  • @Viktor Can you point me to one of those cases? Article I, Section 10 of the Constitution explicitly says, "No state shall... coin money." It also says that they can't "emit bills of credit."
    – reirab
    Commented Feb 14, 2018 at 1:11
  • @reirab see for example en.m.wikipedia.org/wiki/Veazie_Bank_v._Fenno this case recognizes that states may issue their own bank notes, but also that the federal government may tax their use.
    – Viktor
    Commented Feb 14, 2018 at 2:00
  • @Viktor That case appears to be about bank notes rather than coins. At any rate, the ruling in that case does say, "Congress may restrain, by suitable enactments, the circulation as money of any notes not issued under its own authority."
    – reirab
    Commented Feb 14, 2018 at 7:02

Constitutional limits

The federal government has clear jurisdiction over matters that are international or interstate in nature. This is spelled out in the United States constitution, Article I, Section 10:

No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing but gold and silver Coin a Tender in Payment of Debts; pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts, or grant any Title of Nobility.

No State shall, without the Consent of the Congress, lay any Imposts or Duties on Imports or Exports, except what may be absolutely necessary for executing it's inspection Laws: and the net Produce of all Duties and Imposts, laid by any State on Imports or Exports, shall be for the Use of the Treasury of the United States; and all such Laws shall be subject to the Revision and Controul of the Congress.

No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops, or Ships of War in time of Peace, enter into any Agreement or Compact with another State, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay.

This mixes things a bit. Some powers are withheld from both the federal and state governments. For example, bills of attainder, ex post facto law, impairing contracts, and titles of nobility. But the federal government does have the power to create treaties, coin money, set tariffs, and wage war and the states do not.

The rough area of separation is that states have control of most things purely within their borders and the federal government controls most things that cross borders between states or with other countries.

Federal limits

In many areas of commerce, the federal government's power is limited to interstate commerce. From Article I, Section 8 of the constitution:

To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;

This commerce clause means that in some areas of purely intrastate commerce, the federal law does not apply at all. The exact boundaries are often set by precedent and are somewhat flexible in interpretation. For example, Wickard v. Filburn and Gonzalez v. Raich are examples of inclusive interpretations of this clause while US v. Lopez offered a more restrictive view.

Note that other federal powers are less subject to this restraint. For example, the taxing power is not subject to this limitation. Similarly, the power to create post offices is not limited to only carrying mail between states.

Federal supremacy

If state and federal law appear to contradict each other, how is that resolved?

If the federal government can pass laws in a particular area, then its laws are supreme.

This comes from the Supremacy Clause in Article VI of the constitution:

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.

There are some odd results that come from this though.

For example, if a state sets a minimum wage higher than the federal minimum wage, then the state wage would normally hold in that state. This works because the higher state minimum doesn't conflict with the federal law. The federal law does not say that businesses can't pay more but that they can't pay less. So the higher wage usually wins. An exception is if the employee is engaged in interstate commerce, e.g. driving from Midland, Pennsylvania to East Liverpool, Ohio or Chester, West Virginia. Then the state law no longer applies under certain circumstances, as the state can't mandate wages paid for work in other states. Only the federal law would apply.

Another example would be marijuana laws. The case Gonzalez v. Raich held that the federal government was able to make the use of marijuana illegal. So even in states that have legalized marijuana for some or all purposes, it is still illegal under federal law. However, the federal government does not normally prosecute most state level offenses like personal use. It is also unclear what would happen if this case were revisited.

If Anthony Kennedy retires next year, then only three votes will remain from the majority and Trump will have appointed two replacements for Justices from the majority. If the two George W. Bush replacements in the minority vote as their predecessors did, Clarence Thomas votes the same, and the two Trump-appointed replacements vote in line with the federalist view, that would give a majority in the other direction. And that doesn't even consider the possibility that either of the Barack Obama replacements might vote in favor of legalized marijuana.


You're asking a lot of questions there. I'll try and answer a few.

In the US, is there a clear division of responsibility between the kinds of laws that can be passed by the US Congress, compared to the kinds of laws that can be passed by state legislatures?

The primary and clearest division is jurisdiction. A state can only pass laws that pertain to their state, while federal laws apply to all states.

States can also offer more rights to their residents than federal law allows, but they can not take rights away that are already granted by federal law.

This site has a nice comparison chart:


Is this question viewed differently by certain political groups? Is this one of the conservative vs liberal splits?

You will hear the phrase "state's rights" brought up quite a bit, but it's often used more as rhetoric than doctrine and typically is used when a group feels that federal law will prohibit their state from restricting the rights of their citizens as they see fit (see previous point about state laws not being able to restrict rights granted at the federal level).

In the past, Jim Crow laws were often seen as a 'states right' issue in that sense. More recently, gay marriage.

If a state and a federal law appear to contradict each other, which one wins?

Technically, the federal law wins.

Can a state really legalize marijuana?

Despite the above technicality, yes, many have. As of 2017 seven states have legalized it completely, and many more have legalized it for medicinal purposes.

How can that be? Well, it's still illegal under federal law. It's just that the federal entities responsible for enforcing said law have opted to not enforce it in the states that have legalized it.

Can they ban abortion?

Like legalizing marijuana, they likely can. Though they'd likely be in court fairly quickly if they did so.

If a state law and a federal law create different (but not contradictory) regulations about something, how do they interact? For example, if my state's minimum wage is $9.50/hr but the federal minimum wage is $7.25/hr, what is my effective minimum wage?

$9.50. This is an example of your state granting you more rights than the federal law.

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    @BradC I imagine state's marijuana laws cold also be struck down in federal court as well. But I do see the difference here...one is a law trying to be more restrictive while the other is less restrictive than the federal law.
    – user1530
    Commented Nov 20, 2017 at 21:56
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    If a state passed a law banning abortion, lower courts would be forced to strike it down under the precedent of Roe v. Wade. However, if it made its way to the U.S. Supreme Court, Roe v. Wade could be overturned and the state law upheld. Indeed, this would be about the only way to overturn Roe v. Wade barring an amendment to the U.S. Constitution (which seems quite unlikely to happen, given the broad consensus required for an amendment.)
    – reirab
    Commented Nov 20, 2017 at 22:19
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    @Snowman States do try that, but anything that is effectively an abortion ban is struck down.
    – D M
    Commented Nov 20, 2017 at 23:30
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    " "state's rights" ... typically is used when a group feels that federal law will prohibit their state from restricting the rights of their citizens as they see fit" That's not really accurate. It's frequently used for all sorts of things that have nothing to do with states restricting their citizens rights. Indeed, it's sometimes used when the states want to grant more rights than a proposed federal law (e.g. gun control legislation,) but also for federal regulations on everything from schools to roads to environment regulations to commerce regulations, etc.
    – reirab
    Commented Nov 20, 2017 at 23:55
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    For example, libertarians probably argue more strongly for states' rights than any other widespread group and they're also the ones least likely to be trying to impose some limitation on the rights of citizens.
    – reirab
    Commented Nov 20, 2017 at 23:57

In the US, is there a clear division of responsibility between the kinds of laws that are passed by the US Congress, compared to the laws that are passed by state legislatures?

Legally, the federal government can only pass laws related to a power granted by the Constitution. The 10th Amendment says that powers not granted to the federal government are reserved to the states.

In practice, this is extended to things only partially related to a listed power, and the Commerce Clause relates to many areas. The classic example is Wickard v. Filburn, a Supreme Court case from 1942 where limiting how much wheat a farmer could grow was found to be properly regulated as "interstate commerce", even though it was neither interstate nor commerce since he was using the wheat himself, because he might have otherwise bought the wheat. See also Gonzales v. Raich, a Supreme Court case from 2005 stating that the federal government can criminalize marijuana even if a state purports to legalize it.

Is this a widely understood and agreed-upon question? Or is it controversial?

The basics are fairly well understood, but of course the details are controversial. Someone could understandably think it's an overreach for someone growing wheat (or marijuana) for personal use, to be regulated by a law that's supposed to be regulating "interstate commerce". Conservatives are somewhat more likely to think the federal government is more restricted, and liberals are more likely to think the federal government is less restricted.

If state and federal law appear to contradict each other, how is that resolved?

The Supremacy Clause of the Constitution means that federal law will trump state law, if they conflict. In some cases, when Congress passes a law it specifies that states may not pass stricter laws.

Of course, even when they specify, the exact boundaries of what is regulated can come into dispute. A recent example: California attempted to ban the sale of foie gras if it was produced by the forced feeding of geese (even if that feeding occurred in another state), and a company attempted to claim that the state law was preempted by a federal law which said that states cannot impose ingredient requirements different than the federal regulations. The district court agreed that the state law was pre-empted, but the appeals court reversed and said the law was valid because force-feeding was not really an ingredient.

If a state law and a federal law create different (but not contradictory) regulations about something, how do they interact? For example, if my state's minimum wage is $9.50/hr but the federal minimum wage is $7.25/hr, what is my effective minimum wage?

If they don't contradict, both laws can be enforced. If the amounts differ, then it's possible that you'd only be in violation of state law and not federal law (or, if the state minimum was lower, federal law and not state law) but you'd still be in violation of a law unless you met both, so the effective wage would be the higher of the two.

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