Sec. 151.309.  GOVERNMENTAL ENTITIES.  A taxable item sold, leased, or rented to, or stored, used, or consumed by, any of the following governmental entities is exempted from the taxes imposed by this chapter:
(1)  the United States;
(2)  an unincorporated instrumentality of the United States;
(3)  a corporation that is an agency or instrumentality of the United States and is wholly owned by the United States or by another corporation wholly owned by the United States;
(4)  this state;
(5)  a county, city, special district, or other political subdivision of this state;  or
(6)  a state, or a governmental unit of a state that borders this state, but only to the extent that the other state or governmental unit exempts or does not impose a tax on similar sales of items to this state or a political subdivision of this state.
Acts 1981, 67th Leg., p. 1560, ch. 389, Sec. 1, eff. Jan. 1, 1982.  Amended by Acts 1993, 73rd Leg., ch. 719, Sec. 1, eff. July 1, 1993.