Yes, Federal agencies must -
(a) First utilize space in Government-owned and Government-leased buildings; and
(b) If there is no suitable space in Government-owned and Government-leased buildings, utilize space in buildings under the custody and control of the U.S. Postal Service; and
(c) If there is no suitable space in buildings under the custody and control of the U.S. Postal Service, agencies may acquire real estate by lease, purchase, or construction, as specified in part 102-73 of this chapter.