Mont. Code Ann. § 7-13-2343

Any territory included within any district formed under the provisions of this part and part 22 and not benefited in any manner by such district or its continued inclusion therein may be excluded therefrom by order of the board of directors of such district upon the verified petition of the owner or owners in fee of lands whose assessed value, with improvements, is in excess of one-half of the assessed value of all the lands, with improvements, held in private ownership in such territory.