Cal. Evid. Code § 980

Subject to Section 912 and except as otherwise provided in this article, a spouse (or his or her guardian or conservator when he or she has a guardian or conservator), whether or not a party, has a privilege during the marital or domestic partnership relationship and afterwards to refuse to disclose, and to prevent another from disclosing, a communication if he or she claims the privilege and the communication was made in confidence between him or her and the other spouse while they were spouses.