Cal. Elec. Code § 18630

Every person who threatens to commit an assault or battery on a person circulating a referendum, initiative, or recall petition or on a relative of a person circulating a referendum, initiative, or recall petition or to inflict damage on the property of the circulator or the relative, with the intent to dissuade the circulator from circulating the petition or in retribution for the circulation, is guilty of a misdemeanor.