Except for disposals specifically authorized by special legislation, disposals of real property must be made only under the authority of Chapter 5 of Subtitle I of Title 40 of the United States Code. However, the Administrator of General Services can evaluate, on a case-by-case basis, the disposal provisions of any other law to determine consistency with the authority conferred by Title 40. The provisions of this section do not apply to disposals of real property authorized to be made by 40 U.S.C. 113 or by any special statute that directs or requires an Executive agency named in the law to transfer or convey specifically described real property in accordance with the provisions of that statute.