California Code, Business and Professions Code - BPC § 17538.41

(b) This section shall not apply to text messages transmitted at the direction of a person or entity offering mobile telephony service, pager service, or two-way messaging service if the subscriber is offered an option to not receive those text messages.

(c) This section shall not apply to text messages transmitted by a business, candidate, or political committee that has an existing relationship with the subscriber if the subscriber is offered an option not to receive text messages from that business, candidate, or political committee.

(d) This section shall not apply to text messages transmitted by an affiliate of a business that has an existing relationship with the subscriber, but only if the subscriber has provided consent to the business with which he or she has that relationship to receive text messages from affiliates of that business.  “Affiliate” means any company that controls, is controlled by, or is under common control with, another company.

(e) This section shall not apply to electronic mail messages that are forwarded, without the knowledge of the sender, to a mobile telephony services handset, pager, or two-way messaging device.

(f) Subdivision (a) shall not impose an obligation on a person or entity offering mobile telephony service, pager service, or two-way messaging service to control the transmission of a text message unless the message is transmitted at the direction of that person or entity.

(g) For purposes of this section, “mobile telephony service” means commercially available interconnected mobile phone services that provide access to the public switched telephone network (PSTN) via mobile communication devices employing radiowave technology to transmit calls, including cellular radiotelephone, broadband Personal Communications Services (PCS), and digital Specialized Mobile Radio (SMR).