California Code, Public Utilities Code - PUC § 7677

No person, firm, or corporation operating a railroad with more than four trains each way every 24 hours shall require or permit any engineer, fireman, conductor, brakeman, or trainman to receive, deliver, or transmit at any receiving or forwarding instrument of any telegraph or telephone line, any order for the movement of any train, except in such cases or classes of cases as are permitted by the commission. This section does not apply to interurban or street railroads. Any person, firm, or corporation violating this section is guilty of a misdemeanor.