Since 1997, California Evidence Code section 1119 and following have barred the admissibility, discovery or compelled disclosure of statements, admissions or writings made “in the course of, or pursuant to, a mediation or mediation consulting” with only a few exceptions largely involving the parties’ consent, and further providing that “communications, negotiations or settlement discussions by and between participants in the course of a mediation or mediation consultation shall remain confidential.”
For a long time, it has been the practice of mediators to so notify the parties to a mediation and, often, to require them to sign a confidentiality agreement. A typical example of one of these agreements (the one used by Bruce Nye Mediation) is here.
On September 11, Governor Jerry Brown signed Senate Bill 954, effective January 1, 2019, which is designed to increase the likelihood of confidentiality rules being followed.