25 C.F.R. § 162.415
How must a business lease address ownership of permanent improvements?
(a) A business lease must specify who will own any permanent improvements the lessee constructs during the lease term and may specify under what conditions, if any, permanent improvements the lessee constructs may be conveyed to the Indian landowners during the lease term. In addition, the lease must indicate whether each specific permanent improvement the lessee constructs will:
(1) Remain on the leased premises, upon the expiration, cancellation, or termination of the lease, in a condition satisfactory to the Indian landowners, and become the property of the Indian landowners;
(2) Be removed within a time period specified in the lease, at the lessee's expense, with the leased premises to be restored as closely as possible to their condition before construction of the permanent improvements; or
(3) Be disposed of by other specified means.
(b) A lease that requires the lessee to remove the permanent improvements must also provide the Indian landowners with an option to take possession of and title to the permanent improvements if the improvements are not removed within the specified time period.