No person is liable for damages caused by buffalo, horses, cattle, mules, goats, or sheep owned by the person, that trespass upon lands within the exterior boundaries of the Black Hills and Harney National Forests, if the lands were not at the time of the trespass enclosed by a legal fence, as defined in §§ 43-23-3 and 43-23-4.
SDCL 40-28-5