Sec. 161.120.  VALIDITY OF BONDS.  (a)  After the bonds are approved by the attorney general and registered with the state comptroller, they shall be held as valid and binding obligations of the state in every action, suit, or proceeding in which their validity is or may be brought into question.
(b)  In each action brought to enforce collection of the bonds or rights incident to the bonds, the certificate of approval by the attorney general or a certified copy of that certificate shall be admitted and received in evidence as to the validity of the bonds.
(c)  The only defense that can be offered against the validity of the bonds shall be forgery or fraud.
Acts 1977, 65th Leg., p. 2660, ch. 871, art. I, Sec. 1, eff. Sept. 1, 1977.