California Code, Business and Professions Code - BPC § 512

(a) Except as provided in subdivisions (b) and (c), no contract that is issued, amended, renewed, or delivered on or after January 1, 1999, between any person or entity, including, but not limited to, any group of physicians and surgeons, any medical group, any independent practice association (IPA), or any preferred provider organization (PPO), and a health care provider shall contain provisions that prohibit, restrict, or limit the health care provider from advertising.

(b) Nothing in this section shall be construed to prohibit the establishment of reasonable guidelines in connection with the activities regulated pursuant to this division, including those to prevent advertising that is, in whole or in part, untrue, misleading, deceptive, or otherwise inconsistent with this division or the rules and regulations promulgated thereunder. For advertisements mentioning a provider's participation in a plan or product line of any person or entity, nothing in this section shall be construed to prohibit requiring each advertisement to contain a disclaimer to the effect that the provider's services may be covered for some, but not all, plans or product lines of that person or entity, or that the person or entity may cover some, but not all, provider services.

(c) Nothing in this section is intended to prohibit provisions or agreements intended to protect service marks, trademarks, trade secrets, or other confidential information or property. If a health care provider participates on a provider panel or network as a result of a direct contractual arrangement with a person or entity, including, but not limited to, any group of physicians and surgeons, any medical group, any independent practice association, or any preferred provider organization, that, in turn, has entered into a direct contractual arrangement with another person or entity, pursuant to which enrollees, subscribers, insureds, and other beneficiaries of that other person or entity may receive covered services from the health care provider, then nothing in this section is intended to prohibit reasonable provisions or agreements in the direct contractual arrangement between the health care provider and the person or entity that protect the name or trade name of the other person or entity or require that the health care provider obtain the consent of the person or entity prior to the use of the name or trade name of the person or entity in any advertising by the health care provider.

(d) Nothing in this section shall be construed to impair or impede the authority of any state department to regulate advertising, disclosure, or solicitation pursuant to this division.