Wyo. Stat. § 11-33-105: Creation; order; mandatory condition of fences.

The board of county commissioners shall provide as a condition in any order creating a livestock district that the livestock district shall be enclosed by a lawful fence and that any road extending from the livestock district shall contain cattle guards or gates at such places and of such nature as the board prescribes. The board of county commissioners shall make its livestock district orders inapplicable to cattle, horses, sheep or mules straying into the livestock district until the district is enclosed by lawful fence and cattle guards or gates are installed.