No trespassing signs can be useful to property owners—especially on large tracts of land or land that is not developed—to put persons entering the property on notice that the property is private property and if they do not have permission to enter, they may be committing civil and criminal offenses related to trespassing. In some states notice is required for a trespasser to have civil or criminal liability for entering the property without permission.

No trespassing signs may also protect a landowner against liability to a trespasser, as a lower duty of care is owed to trespassers in some states, and putting a person entering the property on notice that they are trespassing may strengthen the property owner’s defense against any liability claims if the trespasser is injured on the property.

In Texas, property owners can use 'no trespassing' signs to deter unauthorized entry and reduce liability. Texas Penal Code Section 30.05 governs criminal trespass and stipulates that a person commits an offense if they enter or remain on property without effective consent and they had notice that the entry was forbidden or received notice to depart but failed to do so. Notice can be verbal, written, or through signage. 'No trespassing' signs serve as a clear written notice, making it a criminal offense for someone to remain on the property without permission. Regarding civil liability, Texas follows the traditional common law categories of entrants to land: invitees, licensees, and trespassers, with the lowest duty of care owed to trespassers. Posting 'no trespassing' signs can help landowners establish that a person was a trespasser, potentially limiting the landowner's liability if a trespasser is injured on the property. However, Texas does have an attractive nuisance doctrine that may impose liability on landowners in certain situations where children are involved, even if 'no trespassing' signs are posted.