Tex. Gov't Code § 832.003
A person terminates membership in the retirement system by:
Acts 1981, 67th Leg., p. 1876, ch. 453, Sec. 1, eff. Sept. 1, 1981. Renumbered from Vernon's Ann.Civ.St. Title 110B, Sec. 42.003 by Acts 1989, 71st Leg., ch. 179, Sec. 1, eff. Sept. 1, 1989.