Cal. Business and Professions Code - BPC § 22940. Section 22940.
It shall be unlawful for any business to use words expressly referencing an individual’s marital status as part of the individual’s mailing address on a billing statement, related correspondence, enclosing envelope, or any solicitation for new business. This shall not prohibit the use of the prefix “Mr.,” “Mrs.,” “Ms.,” or “Miss.”