20 U.S. Code § 76cc - Board of Trustees
(a) Establishment; powers and duties
There is established in the Smithsonian Institution a Board of Trustees to be known as the Trustees of the Joseph H. Hirshhorn Museum and Sculpture Garden, which shall provide advice and assistance to the Board of Regents of the Smithsonian Institution on all matters relating to the administration, operation, maintenance, and preservation of the Joseph H. Hirshhorn Museum and Sculpture Garden; and which shall have the sole authority
(i) to purchase or otherwise acquire (whether by gift, exchange, or other means) works of art for the Joseph H. Hirshhorn Museum and Sculpture Garden,
(iii) to determine policy as to the method of display of the works of art contained in said museum and sculpture garden.
(b) Membership; appointment; terms of office; vacancies
The Board of Trustees shall be composed of the Chief Justice of the United States and the Secretary of the Smithsonian Institution, who shall serve as ex officio members, and eight general members to be appointed as follows: Four of the general members first taking office shall be appointed by the President of the United States from among nominations submitted by Joseph H. Hirshhorn and four shall be appointed by the President from among nominations submitted by the Board of Regents of the Smithsonian Institution. The general members so appointed by the President shall have terms expiring one each on July 1, 1968, 1969, 1970, 1971, 1972, 1973, 1974, and 1975, as designated by the President. Successor general members (who may be elected from among members whose terms have expired) shall serve for a term of six years, except that a successor chosen to fill a vacancy occurring prior to the expiration of the term of office of his predecessor shall be chosen only for the remainder of such term. Vacancies occurring among general members of the Board of Trustees of the Joseph H. Hirshhorn Museum and Sculpture Garden shall be filled by a vote of not less than four-fifths of the then acting members of the Board of Trustees.