The Adjutant General shall be appointed by the Governor from the active or retired commissioned officers of the National Guard of this state. Such Adjutant General shall be or have been a commissioned officer who has actively served in the National Guard of this state for at least five years, shall have attained at least the grade of lieutenant colonel, and shall be able to become eligible for promotion to general officer. If a retired officer is appointed, he or she shall not have been retired for more than two years at the time he or she is considered for appointment. He or she shall hold his or her office as provided in section 55-136. He or she shall receive for his or her services such salary as the Governor shall direct, payable biweekly, except that such salary shall not exceed the annual pay and allowances of regular military officers of equal rank. If funds made available by the federal government are in excess of the amount payable as directed by the Governor, the excess shall be used to reduce the amount required to be paid by the state. Due to the interrelated nature of the Adjutant General's state and federal duties, the Adjutant General shall not be required to take paid or unpaid leave or leaves of absence to perform his or her federal duties, whether or not under federal orders. The Adjutant General shall continue to receive his or her salary during all such periods. The Adjutant General shall only be required to take leave or leaves of absence during those times when he or she is absent and performing neither his or her state nor federal duties as Adjutant General. This section shall not apply if the Adjutant General is called to active duty of the United States under 10 U.S.C.