Pursuant to the authority of section 413 of this title, the Secretary shall withhold a reasonable deduction from the gross proceeds of sales of forest products harvested from Indian forest land under a timber sale contract, permit, or other harvest sale document, which has been approved by the Secretary, to cover in whole or part the cost of managing and protecting such Indian forest land.
Deductions made pursuant to subsection (a) shall not exceed the lesser amount of-
unless the appropriate Indian tribe consents to an increase in the deductions.
The full amount of any deduction collected by the Secretary shall be expended according to an approved expenditure plan, approved by the Secretary and the appropriate Indian tribe, for the performance of forest land management activities on the reservation from which such deductions are collected and shall be made available to the tribe, upon its request, by contract or agreement for the performance of such activities.
25 U.S.C. § 3105