Cal. Pub. Util. Code § 13164

From and after the issuance of any issue of bonds the findings and determinations of the board respecting that issue made pursuant to this article shall be conclusive evidence of the existence of the facts so found and determined in any action or proceeding in any court in which the validity of such bonds is at issue, and no bona fide purchaser of any such bond containing the certification and recital permitted by this article shall be required to see to the existence of any fact, or to the performance of any condition, or the taking of any proceeding, required prior to such issue, or to the application of the purchase price paid for such bonds.