Chief of National Guard Bureau: appointment; actinsf chief (a) The President, by and with the advice and consent of the Senate, shall appoint the Chief of the National Guard Bureau from ofl&cers of the Army National Guard of the United States or the Air National Guard of the United States who— (1) have been recommended by their respective governors; (2) have had at least 10 years of commissioned service in the active National Guard; and (3) are in a grade above lieutenant colonel. (b) The Chief of the National Guard Bureau holds office for four years, but may be removed for cause at any time and may not hold that office after he becomes 64 years of age. H e is eligible to succeed himself. If he holds a lower reserve grade he shall be appointed as a Reserve in his armed force in the grade of major general for service in the Army National Guard of the United States or the Air National Guard of the United States, as the case may be. (c) If the Chief of the National Guard Bureau is unable, because of disability, to perform the functions of his office, or if that office is vacant, the senior officer of the Army National Guard of the United States or the Air National Guard of the United States on duty in the Bureau shall act as its chief until the disability ceases or a successor is appointed. § 3016. Administrative Assistant (a) There is an Administrative Assistant in the Department of the Army. The Administrative Assistant shall be appointed by the Secretary of the Army and shall perform duties that the Secretary considers appropriate. (b) During a vacancy in the office of Secretary, the Administrative Assistant has charge and custody of all records, books, and papers of the Department of the Army. (c) The Secretary may authorize the Administrative Assistant to sign, during the temporary absence of the Secretary, any paper requiring his signature. I n such a case, the Administrative Assistant's signature has the same effect as the Secretary's signature. § 3017. Secretary of the Army: successors to duties (a) If the Secretary of the Army dies, resigns, is removed from office, is absent, or is disabled, the person who is highest on the following list, and who is not absent or disabled, shall perform the duties of the Secretary until the President, under section 6 of title 5, directs another person to perform those duties or until the absence or disability ceases: (1) The Under Secretary of the Army. (2) The Assistant Secretaries of the Army in order of their length of service as such. (3) The Chief of Staff. (b) Performance of the duties of the Secretary by the Chief of Staff or any officer of the Army designated under section 6 of title 5 shall not be considered as the holding of a civil office within the meaning of section 3544(b) of this title.