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 Wyoming, property owners can use 'no trespassing' signs to deter unauthorized entry and reduce liability. Wyoming statutes require that landowners post signs or use other methods to notify individuals that they are entering private property. According to Wyoming Statute § 6-3-303, a person is guilty of criminal trespass if they enter or remain on the property without the owner's consent and if the property is posted. The signs must be conspicuous and designed to reasonably notify all entrants that they are entering private land. The presence of these signs can establish that a trespasser has entered the property knowingly, which is necessary for criminal liability. Additionally, Wyoming follows the general rule that landowners owe a lower duty of care to trespassers than to invitees or licensees. Therefore, posting 'no trespassing' signs may also help landowners defend against liability claims if a trespasser is injured on their property, as it demonstrates that the trespasser was warned and entered without permission.