Idaho Code § 62-1201
The public utilities commission shall have the jurisdiction and authority to require every railroad company or corporation operating any steam or electric railroad in this state to erect and maintain lawful fences on each or either side of such railroad where such railroad is not now required by law to erect and maintain fences, at such places as the public utilities commission shall determine such fences to be necessary to protect cattle, horses or mules or any other domestic animal being ranged or grazed upon land adjacent to such railroad from being wounded, maimed or killed by the operation or management of engines, cars or other rolling stock upon or over such railroad, with necessary openings and gates in such fences, and crossings and cattle guards for such openings and gates.
Idaho Code § 62-1201