20 U.S.C. § 71a

The Trustees of the National Gallery of Art are authorized to construct within the area reserved as a site for future additions by the third sentence of section 71 of this title one or more buildings to serve as additions to the National Gallery of Art. The cost of constructing any such building shall be paid from trust funds administered by such Trustees. The plans and specifications for any such building shall be approved by the Commission of Fine Arts and the National Capital Planning Commission.