Mont. Code Ann. § 85-1-122

The waters of the Clark Fork River may be impounded or restrained within the state of Montana for a distance not exceeding 25 miles from the Idaho-Montana boundary line by a dam located on said river in the state of Idaho and constructed by any person, firm, partnership, or corporation authorized to do business in the state of Montana. Any present or future appropriations of water in the watershed in the state of Montana for irrigation and domestic use above said dam shall have priority over water for power use at said dam.