For example, why signage in national parks says "it's unlawful to feed wildlife" instead of illegal?

  • 3
    The latter is more pretentious. Commented Jul 31, 2015 at 12:29

3 Answers 3


In United States criminal law there is no difference between "illegal" and "unlawful." Mostly this is because of something called "substantive due process," a right which is guaranteed under the 14th Amendment and which (in part) demands that laws must not be so vague as to leave someone unsure of whether his actions are criminal. In particular, any law must enumerate which acts it is making illegal. So says the United States Supreme Court in Connally v General Construction Co. 269US385 (1926).

Since the rule on the sign prohibiting the feeding of park wildlife seems clear, perhaps the issue is whether violating the rule is tantamount to violating the law. And so it is. Step right up to 16 USC §3 - Rules and regulations of national parks, reservations, and monuments:

The Secretary of the Interior shall make and publish such rules and regulations as he may deem necessary or proper for the use and management of the parks, monuments, and reservations under the jurisdiction of the National Park Service, and any violation of any of the rules and regulations authorized by this section and sections 1, 2, and 4 of this title shall be punished by a fine of not more than $500 or imprisonment for not exceeding six months, or both,....

The principle here has a Latin description nulla poena sine lege, meaning "no punishment without the law," and is usually interpreted to mean that laws must be "praevia, scripta, certa, stricta", i.e., enacted previous to the offense, written down, certain in description, and strictly interpreted. A brief time spent in the google leads me to believe this is the way modern law works in Europe (including Great Britain), but I'm out of my depth on that subject.


There is no difference in meaning.

In this case, "unlawful" is a synonym of "illegal." The sign could just as well read "it's illegal to feed wildlife" – it would mean the same thing to the vast majority of people.

The first definition the Merriam-Webster online dictionary gives for unlawful:

not lawful : illegal


In the context of this sign and the US Park Service, there may be no difference between "unlawful" and "illegal".

Some laws prohibit certain activities, making them illegal, i.e. against the law. Most of the time there are penalties or sanctions against illegal activity.

Outside of criminal law, some laws prescribe or specify certain activities. For example, contract law specifies what constitutes a valid contract. If a contract is executed according to that specification, then it is a lawful contract. An unlawful contract fails on one or more counts in the specification. It isn't illegal, however. Just not enforceable.

  • This answer clarified the difference between lawful and legal for me, but the sign cited in the question doesn't seem to fit. Any thoughts?
    – rabbit
    Commented Jul 31, 2015 at 5:26
  • @rabbit Many times, maybe even most of the time, the people writing these signs are not lawyers and instead tend to follow convention, i.e. what other people like them did before. In this case, there may not be any law that makes feeding wildlife illegal. It might instead be a regulation of the National Park Service, which is part of the Executive Branch of government. These regulations will include many allowed and prohibited activities, including perhaps feeding wildlife. If so, it would be more accurate for the sign to say "USPS regulations prohibit feeding...". Commented Jul 31, 2015 at 5:41
  • @sumelic Yes, people use the two words interchangeably. Including dictionaries. Does that mean there is no difference in meaning? I think not. Is a contract that fails by one or more criteria to be valid an illegal contract? No, it isn't. It is unlawful and unenforceable, but it is not illegal. --- There are some legal systems, like the old Soviet Union, where everything not explicitly permitted in law was prohibited, i.e. illegal. "unlawful" == "illegal" Commented Jul 31, 2015 at 7:40
  • The Grammarphobia blog has a post that mentions this exact distinction, in the context of contract law: grammarphobia.com/blog/2013/07/illegal-unlawful.html
    – herisson
    Commented Jul 31, 2015 at 7:54
  • @sumelic Well then! +1 to me! whoo hoo! Commented Jul 31, 2015 at 7:56

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