16 U.S. Code § 6206 - Cabin user fees
(a) In general
The Secretary shall establish the cabin user fee as the amount that is equal to 5 percent of the market value of the lot, as determined in accordance with section 6205 of this title, reflecting an adjustment to the typical market rate of return due to restrictions imposed by the permit, including—
(b) Fee for caretaker cabin
The base cabin user fee for a lot on which a caretaker cabin is located shall not be greater than the base cabin user fee charged for the authorized use of a similar typical lot in the tract.
(c) Annual cabin user fee in the event of determination not to reissue authorization
If the Secretary determines that an authorization should not be reissued at the end of a term, the Secretary shall—
(1) establish as the new base cabin user fee for the remaining term of the authorization the amount charged as the cabin user fee in the year that was 10 years before the year in which the authorization expires; and
(d) Annual cabin user fee in event of changed conditions
If a review of a decision to convert a lot to an alternative public use indicates that the continuation of the authorization for use and occupancy of the cabin by the cabin owner is warranted, and the decision is subsequently reversed, the Secretary may require the cabin owner to pay any portion of annual cabin user fees that were forgone as a result of the expectation of termination of use and occupancy of the cabin by the cabin owner.
(e) Termination of fee obligation in loss resulting from acts of God or catastrophic events
On a determination by the agency that, because of an act of God or a catastrophic event, a lot cannot be safely occupied and the authorization for the lot should accordingly be terminated, the fee obligation of the cabin owner shall terminate effective on the date of the occurrence of the act or event.