(a) Bonds issued by a district must be submitted to the attorney general for examination.
(b) If the attorney general finds that the bonds have been authorized in accordance with law, the attorney general shall approve them. On approval by the attorney general, the comptroller shall register the bonds.

(c) After the approval and registration of bonds, the bonds are incontestable in any court or other forum for any reason and are valid and binding obligations according to their terms for all purposes.