California Code, Labor Code - LAB § 1110

No agreement, combination, or contract, by or between two or more persons to do or procure to be done, or not to do or procure not to be done, any act in contemplation or furtherance of any trade dispute between employers and employees in the State is criminal, if the same act committed by one person would not be punishable as a crime. This chapter does not authorize violence, or threats thereof.