In U.S. politics what is the difference between something being illegal vs unconstitutional?

My current understanding (as a non-US person):

  • Wouldn't something illegal automatically be unconstitutional (laws flow from the constitution), the legality overrides the constitutionality.
  • If something is unconstitutional there isn't necessarily a law making it illegal, as a matter of practicality.
  • 1
    The American legal code is separate from the constitution, though it cannot violate the limits set in the constitution.
    – Publius
    Mar 31 '13 at 18:11

Generally speaking, in the U.S. actions are said to be "illegal" whereas laws are said to be "unconstitutional." I think a confusion arises because in the U.S. the term "Constitution" (capital C) refers specifically to the written document, whereas in countries like the UK without such a document the term "constitution" (lowercase C) refers to the entire body of principles and laws that define the government. In the U.S., laws passed by Congress are not considered to be part of the Constitution; indeed, the Constitution places limits on the types of laws they can pass to begin with.

The U.S. Constitution is considered to be the supreme law of the land. Therefore, any law passed in contradiction to the Constitution (including its various amendments) is automatically considered invalid. Since Marbury v. Madison the courts have claimed the right to declare laws unconstitutional, rendering those laws unenforceable. At various points in U.S. history, individual states also controversially claimed the right to ignore laws they deemed unconstitutional, which was known as nullification.

One way that a federal law can be unconstitutional is if it falls outside the enumerated powers of the federal government set fourth in the Constitution (or in any amendment, since amendments are part of the Constitution). Since the framers of the Constitution were worried about the federal government overpowering the states, they limited Congress to only passing laws with respect to certain subjects that were considered to affect the entire nation. These areas include interstate commerce, national defense, and the creation of money (according to the Tenth Amendment, all other powers are reserved to the states or to the people). Conversely, state laws can be unconstitutional if they interfere with a legitimate power of the federal government or attempt to exercise a power (such as the coinage of money) that the Constitution explicitly forbids them.

Another way that a law can be unconstitutional is if it infringes on the basic rights of the citizenry. These include, most notably, the ones set forth in the Bill of Rights; however, the Ninth Amendment specifies that the rights of the people are not limited to those specifically enumerated in that document.

If Congress or the states disagree with the court's interpretation of the Constitution then they can pass a constitutional amendment. However, since amendments require the consent of three-quarters of the states for ratification, they are seldom used.

That is my understanding of the matter.

  • 3
    This is generally a good answer, but the opening generalization is perhaps a bit too strong. A government action can be unconstitutional. For example, if a police officer searches someone without a good reason, it is an unconstitutional search.
    – phoog
    Jul 25 '18 at 16:48

Illegal means it is against the law and there are civil or criminal penalties associated with it. However there is nothing in the constitution that would prohibit the sale/consumption of alcohol by minors (just an easy example). In fact until 1919 only a few states had any drinking age limit. This is a law but neither barring it nor allowing it violates the constitution.

There are things that are unconstitutional that are not illegal. For instance there is no penalty for members of congress or a president for passing/signing a law that blatantly infringes a constitutionally protected right. There are not penalties associated with violating the constitution.

The Constitution is written as a limit and basic guide for running the government of the United States. It provides the limits of the power and provides some activities where the government has responsibilities. Laws are written as limits on individuals. Part of the codification of laws is including the penalties that may be prescribed in the event of violation, as well as exemptions to the law. For instance the killing of another person through violence is illegal. However there is an exemption if you are in imminent danger from the person and are unable to escape.

  • 6
    Constitution is a META law.
    – user4012
    Apr 1 '13 at 17:26
  • @DVK the constution has some meta laws, but it's not all meta laws. There are laws regarding how new states are added, there are laws regarding how electors are elected, there are laws requiring you to have available access to an attorney, There are laws requiring people convicted in one state, to be returned to that state to be tried, There was even once a law prohibiting the sale of alcohol Apr 1 '13 at 18:32
  • Might be better to think of it as "the laws the government has to follow" as opposed to "the laws that individuals have to follow, even as they go about conducting government business".
    – Bobson
    Oct 30 '19 at 21:38

In the United States (and most other countries) there are multiple sources of law. The Constitution, statute, court decisions, executive proclamations, and more are all examples of 'law'.

See this introductory guide for some high-level basics (from the University of Idaho law school). For a more in-depth guide, the Cornell Law School has provided this 'order of authorities'.


The Constitution is one source of law. When something is done in violation of the Constitution it is "unconstitutional". Legal vocabulary aside, that term means exactly what it says: contrary to the Constitution.

Because the Constitution is a source of law, everything that is unconstitutional is also illegal.

Additionally, there are state constitutions as well. So "unconstitutional" could also mean contrary to the constitution of a specific state within the United States


Statutes are laws written by legislatures. This includes municipal laws passed by a city council, those passed by state legislatures, as well as Congress. Not everything passed by a legislature is a statute, for example legislatures often pass resolutions which do not have the force of law.

Statutes are laws. So anything that is contrary to statute is illegal. However, statutes are not the same as a constitution, so not everything that is illegal is unconstitutional.

Other Sources of Law

There are many other sources of law, and violating the terms of those could also be called "illegal". For example, a court order is a source of law and breaking the terms of a court order is illegal. The same goes for international treaties, executive proclamations, etc.


Here's a simple way to understand the difference. Let's look at one of the more well known parts of the US constitution, the first amendment, which forms a part of the constitution known as the Bill of Rights. These are guarantees the US government makes to it's citizens... they don't say what the government can do, they say what the government cannot do.

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.

There is nothing enforceable on a citizen in this. It doesn't specify penalties for violating any part of the statement. It simply says that congress cannot make laws meeting those conditions, which means that those conditions cannot become illegal.

Illegal means that a given activity by a person, group, or organization violates a law.

Unconstitutional means that a law violates conditions laid down in the constitution, and therefore is not a law and is not enforceable... as applied by the independent judiciary, all the way up to the supreme court.

The constitution is essentially laws that govern the making of laws. A law that was passed by the government can't by itself be illegal, while you as a citizen can't commit an unconstitutional act.


Maybe it is just the state of our affairs here in America, but it becomes hard to read carbon copy answers to every inquiry on our Constitution. I am not putting anyone answer below or above any other, or saying any one is more or less right either. I have a black/white view on this, as there is no room for any gray area as far as anyone's rights are concerned, especially at this time. Illegality would involve a crime. That is it. Crime requires a breach of the peace offense. Crimes require a cop witness you commit a felony, damage property, injure a person, or have an oath signed by a judge, or signed statement from a reliable witness of you doing any one of these things. (https://supreme.justia.com/cases/federal/us/440/648/) That is it. Everything else is a state statute, or city code or ordinance, which, as much as they would like them to be, are not, and will never be law.( Hall v State SW 2d 363, 326 Ark 318 ) No matter how much they are used, or how accepted they become, statutes, codes, ordinances or local policy never becomes law,or gains authority by acceptance or usage.

Our Constitution is a group of restrictions on our government's scope of powers and authority. (https://www.whitehouse.gov/about-the-white-house/the-constitution/) It is not hard to see how, having a belief of anything other than this, could cause the government to begin to slowly chip away at these rights, mostly unnoticed, and slowly set new rules, laws, and precedence in place until their authority becomes self-perpetuated, and they no longer believe their power is derived from, we the people, and to protect the interests of the same. When you see all of congress, and every other government official participating in even one closed door vote or meeting, or going against what the majority of their district has said they wanted on a certain issue, you had better believe they have replaced their required duty, and sworn to do upon an oath, to represent their citizen's interests, and not the interests of their own, another official, or a corporation. They have traded the protection of our rights for the revenue generating system it has become. These people are the ones in charge of making the laws.

So, though we all have Constitutional rights, these people have made it so if a person doesn't know how to assert these rights, the courts do not recognize these rights. And even if they did, and not found in the constitution, the courts have giving themselves immunity from liability for violating your civil rights, and that self made immunity could be, if not checked soon, the absolute beginning of the end of both our beloved Constitution and our way of life. True, all laws do have to stay within the bounds of the Constitution, and as we go down the list, (ie: state then city, etc.)these next ones are required to protect all persons rights equally, but are allowed to expand these rights as to allow more privileges and protections of these rights. (https://law.justia.com/constitution/us/amendment-14/12-enforcement.html&sa=U&ved=2ahUKEwiqkPT_68TlAhWVtZ4KHU9kCRYQFjAEegQIAxAB&usg=AOvVaw1nDB2JY1mx-3G0Kj9tcVt3) I hope I was able to give you a different way to look at that question, and encourage you to look everywhere for more answers. Knowledge is not power. That is a misconception. Knowledge is potential power, and the more you have, the better you can defend both yours, and others rights better in the future.

  • 3
    "Crimes require a cop witness you commit a felony, damage property, injure a person, or have an oath signed by a judge, or signed statement from a reliable witness of you doing any one of these things. " So if nobody sees me kill someone, no crime was committed?
    – David Rice
    Jul 25 '18 at 16:12
  • 1
    Thanks for putting your thoughts into words. However, this is not a discussion forum. Answers are expected to be factual answers to questions. Can you provide a reference showing that this interpretation is the actual, factual answer, rather than your interpretation? Jul 25 '18 at 16:23
  • 1
    "Illegality would involve a crime." Many activities, such as breaching a contract or negligently harming someone in an accident, are illegal, but are not crimes.
    – ohwilleke
    Jul 28 '18 at 18:16
  • @SoylentGray The standard of liability for criminal negligence is much higher than the standard of negligence for civil liability. Criminal negligence roughly equates to what in a civil case would be called "gross negligence."
    – ohwilleke
    Jul 29 '18 at 0:01

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