The more I've thought about my question about no-trespassing signs saying "POSTED", I've realized that "no trespassing" doesn't really make sense either. Trespassing is, by definition, illegal, making "no trespassing" a tautology. Saying "no trespassing" is equivalent to putting a "no stealing" sign on a car or a "no speeding" sign on a road. "No trespassing" is a true statement anywhere, even if the public is allowed, because if everyone is allowed to be on the property, nobody is trespassing, making "no trespassing" an irrelevant statement, just as a "no stealing" sign on a car is irrelevant to someone who is not stealing it and a "no speeding" sign is irrelevant to someone who is driving at the speed limit.

Why do some private property signs say "no trespassing"? "Private Property" seems like the most logical wording in cases where "POSTED" is not legally necessary, and while it is common, "no trespassing" is also quite common.

2 Answers 2


Trespassing requires knowledge by the trespasser

If you are on somebody’s land without knowing you are, or under the impression (which is the default for unenclosed land) that you have permission, you aren’t trespassing. The signs, if prominent enough, make the entry knowingly against the wishes of the controller and therefore trespassing.

  • I know trespassing requires knowledge; I was asking why the signs say "no trespassing" and not something like "private property" or "keep out".
    – Someone
    Commented Aug 14, 2022 at 15:51
  • @Someone Pretty sure you can find signs that say both. I'm certain I've seen signs with "No Trespassing" in big red letters, and in smaller black letters beneath it "private property", and things of that nature. Which sign gets used is basically a matter of taste by the one posting them, but may be regulated by local law. Commented Aug 14, 2022 at 18:19

Criminal charges for trespassing, ot civil suits for trespassing, in many jurisdictions requiere that the trespasser not only know that s/he is on private property, but that s/he know that an intruding presence is unwelcome. This can be effected by a personal, face-to-face request to leave, by a written notice mailed or otherwise delivered to the future trespasser, by a fence or other enclosure, or by a sign.Which of these methods is legally effective depends on the laws od th jurisdiction involved. Where reliance is on a sign or signs, the law may specify a minimum size a minimum type size, specific wording, or other aspects. Compliant signs are automatically recognized as a valid notice, and if ignored, allow legal action to be taken. Non-compliant signs may not be effective at all, or may require a court to asses whether the signs gave sufficient notice to the intruder that intrusion was not permitted, and the intruder was warned not to enter, or to leave.

All this will vary with specific state or local laws. Using signs that comply with local law, whatever that may specify, avoids arguments about whether the intruder was sufficiently warned. Compliant signs are presumed to be sufficient warning.

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