Cal. Evid. Code § 980

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