Mont. Code Ann. § 20-3-308
Vacancy of trustee position
20-3-308 . Vacancy of trustee position. (1) An elected trustee position is vacant whenever the incumbent:
(a) dies;
(b) resigns;
(c) moves the trustee's residence from the applicable district or from the nominating district in the case of an additional trustee in a high school district;
(d) is no longer a registered elector of the district under the provisions of 20-20-301 ;
(e) is absent from the district for 60 consecutive days;
(f) fails to attend three consecutive meetings of the trustees without a good excuse;
(g) has been removed under the provisions of 20-3-310 ; or
(h) ceases to have the capacity to hold office under any other provision of law.
(2) A trustee position is also vacant when an elected candidate fails to qualify under the provisions of 20-3-307 .