Cal. Pub. Util. Code § 99369

All bonds issued in pursuance of the provisions of this article shall by their issuance be conclusive evidence of the regularity, validity and legal sufficiency of all proceedings, acts and determinations in any wise pertaining thereto, had or made hereunder; and, after the same have been issued, no sales tax levied or collected for the purpose of paying the principal or interest on the bonds shall be held to be invalid or illegal, or set aside by reason of any error, informality, irregularity, omission or defect in any of the proceedings, acts or determinations in any wise pertaining to the issuance or payment of the bonds, and not amounting to a want of due process of law under the Constitution.