Cal. Penal Code § 637

Every person not a party to a telegraphic or telephonic communication who willfully discloses the contents of a telegraphic or telephonic message, or any part thereof, addressed to another person, without the permission of that person, unless directed so to do by the lawful order of a court, is punishable by imprisonment pursuant to subdivision (h) of Section 1170, or in a county jail not exceeding one year, or by fine not exceeding five thousand dollars ($5,000), or by both that fine and imprisonment.