The concessioner may not assign, sell, convey, grant, contract for, or otherwise transfer (such transactions collectively referred to as ``assignments'' 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 the performance of 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.