D.C. Code § 6-1206
That the real property, together with all structures thereon on September 21, 1966, described as lot 800, square 1186, of the District of Columbia, commonly known as the Old Georgetown Market, is hereby declared a historic landmark, and the Mayor of the District of Columbia is authorized and directed to preserve such property as a historic landmark and to operate and maintain it as a public market, except that the Mayor is authorized to enter into an agreement with the Secretary of the Interior to provide for the use of a portion of such property as a museum to be operated by the Secretary in connection with the Chesapeake and Ohio Canal. Such property shall not be used under authority of any provision of law for any purpose not provided in this section unless:
D.C. Code § 6-1206