(a) Except as provided by Subsection (c), an officer is eligible for appointment by the director to chief of the Texas Rangers only if the officer has at least five years of supervisory experience as a commissioned member of the Texas Rangers.
(b) Except as provided by Subsection (c), an officer is eligible for appointment by the director to assistant chief of the Texas Rangers only if the officer has at least four years of supervisory experience as a commissioned member of the Texas Rangers.

(c) If there are fewer than two qualified officers for appointment to chief or assistant chief of the Texas Rangers, the director may appoint an officer to the position of chief or assistant chief of the Texas Rangers only if the officer has at least two years of supervisory experience as a commissioned member of the Texas Rangers.
(d) Except as provided by Subsection (e), an officer is eligible for appointment by the director to the rank of major of the Texas Rangers only if the officer has at least one year of supervisory experience as a captain of the Texas Rangers.
(e) If there are fewer than two qualified captains for appointment to the rank of major of the Texas Rangers, the director may appoint a lieutenant to the position of major of the Texas Rangers only if the lieutenant has at least two years of supervisory experience as a commissioned member of the Texas Rangers.