Cal. Code Civ. Proc. § 430.80 : CALIFORNIA CODE OF CIVIL PROCEDURE — OF CIVIL ACTIONS — OF THE PLEADINGS IN CIVIL ACTIONS — OBJECTIONS TO PLEADINGS; DENIALS AND DEFENSES — OBJECTIONS TO PLEADINGS — Failure to object deemed waiver of objection
(a) If the party against whom a complaint or cross-complaint has been filed fails to object to the pleading, either by demurrer or answer, that party is deemed to have waived the objection unless it is an objection that the court has no jurisdiction of the subject of the cause of action alleged in the pleading or an objection that the pleading does not state facts sufficient to constitute a cause of action.
(b) If the party against whom an answer has been filed fails to demur thereto, that party is deemed to have waived the objection unless it is an objection that the answer does not state facts sufficient to constitute a defense.