California Code, Evidence Code - EVID § 1121

Neither a mediator nor anyone else may submit to a court or other adjudicative body, and a court or other adjudicative body may not consider, any report, assessment, evaluation, recommendation, or finding of any kind by the mediator concerning a mediation conducted by the mediator, other than a report that is mandated by court rule or other law and that states only whether an agreement was reached, unless all parties to the mediation expressly agree otherwise in writing, or orally in accordance with Section 1118.