Mont. Code § 85-7-1832
The petition for this purpose must be signed by at least 75%, both in number and in acreage, of the holders of title or evidence of title (evidence as provided in 85-7-101 and 85-7-102 ) of the lands proposed to be eliminated from one district and incorporated in another existing district or in a new and separate district. Such petition must also bear the signature of the secretary of the interior of the United States, approving such proposed changes in district organization. Construction costs and other obligations due or to become due to the United States on account of the lands so separated and the participation of the owners thereof in contracts in effect between the original district and the United States or between the district to be extended by the addition of said lands and the United States shall be fixed and determined by said secretary of the interior.
§ 85-7-1832, MCA