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 North Dakota, the use of 'no trespassing' signs is recognized as a legitimate way for property owners to notify individuals that they are entering private property and that unauthorized entry is not permitted. According to North Dakota Century Code (NDCC) 12.1-22-03, an individual may be guilty of criminal trespass if they enter or remain on property without authorization and after notice against trespass has been given. Notice can be given in various forms, including personal communication, posting of signs, or fencing that indicates the exclusion of intruders. The presence of 'no trespassing' signs can serve as this notice, making it clear that entry is not allowed, which is essential for establishing both civil and criminal liability for trespass. Furthermore, under North Dakota law, property owners generally owe a lower duty of care to trespassers compared to invitees or licensees. Therefore, posting 'no trespassing' signs may also help landowners reduce their liability in the event that a trespasser is injured on their property, as it demonstrates that the trespasser entered without permission and was warned of the private nature of the property.