Wyo. Stat. § 31-5-113: Placement and maintenance of traffic-control devices by department.

(a) The department shall place and maintain such traffic-control devices, conforming to the department's manual and specifications, upon all state highways as it deems necessary to indicate and to carry out this act or to regulate, warn or guide traffic.

(b) No local authority shall place or maintain any traffic-control device upon any highway under the jurisdiction of the highway department except with the highway department's permission.