36 C.F.R. § 51.86

What encumbrances require the approval of the Director?

        The concessioner may not encumber, pledge, mortgage or otherwise provide as a security interest for any purpose (such transactions collectively referred to as “encumbrances” for purposes of this part), without the prior written approval of the Director, any of the following:

        (a) Any concession contract;

        (b) Any rights to operate under or manage performance under a concession contract as a subconcessioner or otherwise;

        (c) Any controlling interest in a concessioner or concession contract; or

        (d) Any leasehold surrender interest or possessory interest obtained under a concession contract.

Official source