Mont. Code Ann. § 77-6-502
Grazing leases
77-6-502 . Grazing leases. (1) The rental rate for leasing all state grazing lands must attain full market value based upon the appraised animal-unit-month carrying capacity of the land as provided in 77-6-507 .
(2) If the board raises the rentals for state grazing lands during the term of any leases of grazing land that are not issued as a result of competitive bidding, the lessee shall, for the years after the increase becomes effective, pay the increased rental, and the terms of grazing leases must provide for the increase.