81-4-101. Legal fences defined. Except as provided in subsections (2) and (7), a legal fence must be at least 42 inches but not more than 48 inches in height. The following are legal fences in Montana:
(1) fences constructed of at least three barbed, horizontal, well-stretched wires, the lowest of which is not less than 15 inches or more than 18 inches from the ground, securely fastened as nearly equidistant as possible to substantial posts firmly set in the ground or to well-supported leaning posts not exceeding 20 feet apart or 33 feet apart where two or more stays or pickets are used equidistant between posts;
(2) (a) corral fences that are used exclusively for the purposes of enclosing stacks situated outside of any lawful enclosure and that:
(i) are not less than 16 feet from the enclosed stack;
(ii) are substantially built with posts not more than 8 feet distant from each other; and
(iii) consist of at least five strands of well-stretched barbed wire not less than 5 or more than 6 feet high;
(b) a fence as effectual for the purpose of a corral fence as the type described in subsection (2)(a);
(3) fences constructed of any standard woven wire, securely fastened to substantial posts not more than 30 feet apart, with two equidistant barbed wires placed above the woven wire;
(4) other fences made of barbed wire, which must be as strong and as well calculated to protect enclosures as those in subsections (1) through (3);
(5) fences consisting of four boards, rails, or poles with standing or leaning posts not over 17 feet and 6 inches apart and, if leaning posts are used, a pole or wire fastened securely on the inside of the leg or support of each leaning post;
(6) electric fences consisting of three or more wires; and
(7) rivers, hedges, mountain ridges and bluffs, or other barriers over or through which it is impossible for stock to pass.