(a) Bonds and notes issued by a district must be submitted to the attorney general for examination.
(b) If the attorney general finds that the bonds or notes have been authorized in accordance with law, the attorney general shall approve them, and they shall be registered by the comptroller.
(c) After the approval and registration of bonds or notes, the bonds or notes are incontestable in any court or other forum, for any reason, and are valid and binding obligations in accordance with their terms for all purposes.