Mont. Code § 85-7-2115
If a landowner objects to the proceedings of the board in determining the irrigable area in the landowner's own or any other tract of land or the amount or rate per acre of the special tax and assessment to be levied against each irrigable acre in the district or subdistrict for the purposes of the proposed bond issue and the objection is overruled by the board, the objection without further proceedings must be regarded as appealed to the district court. When confirmed, the order overruling the objection and confirming the order of the board determining the irrigable area of each tract of land and apportioning the cost of the improvement to each tract becomes final, binding, and conclusive upon the landowner and upon the district unless appealed.
§ 85-7-2115, MCA