Cal. Civ. Code § 407.040

1. When it appears to the attorney general that a person has engaged in or is engaging in any method, act, use, practice or solicitation declared to be unlawful by this chapter or when he believes it to be in the public interest that an investigation should be made to ascertain whether a person in fact has engaged in or is engaging in any such method, act, use, practice or solicitation, he may execute in writing and cause to be served upon any person who is believed to have information, documentary material, or physical evidence relevant to the alleged or suspected violation, a civil investigative demand requiring such person to appear and testify, or to produce relevant documentary material or physical evidence or examination, at such reasonable time and place as may be stated in the civil investigative demand, concerning the advertisement, sale or offering for sale of any goods or services or the conduct of any trade or commerce or the conduct of any solicitation that is the subject matter of the investigation. Service of any civil investigative demand, notice, or subpoena may be made by any person authorized by law to serve process or by any duly authorized employee of the attorney general.

2. Each civil investigative demand shall:

(1) State the statute and section thereof, the alleged violation of which is under investigation, and the general subject matter of the investigation;

(2) Describe the class or classes of information, documentary material, or physical evidence to be produced thereunder with reasonable specificity so as fairly to indicate the material demanded;

(3) Prescribe a return date by which the information, documentary material, or physical evidence is to be produced; and

(4) Identify the members of the attorney general's staff to whom the information, documentary material, or physical evidence requested is to be made available.

3. No civil investigative demand shall:

(1) Contain any requirement which would be unreasonable or improper if contained in a subpoena duces tecum issued by a court of this state; or

(2) Require the disclosure of any documentary material which would be privileged or which, for any other reason, could not be required by a subpoena duces tecum issued by a court of this state.

4. Service of any civil investigative demand, notice, or subpoena may be made by:

(1) Delivering a duly executed copy thereof to the person to be served, or to a partner or any officer or agent authorized by appointment or by law to receive service of process on behalf of such person;

(2) Delivering a duly executed copy thereof to the principal place of business or the residence in this state of the person to be served;

(3) Mailing by registered or certified mail a duly executed copy thereof, addressed to the person to be served, at the principal place of business or the residence in this state or, if such person has no place of business or residence in this state, to his principal office or place of business or his residence; or

(4) The mailing thereof by registered or certified mail, requesting a return receipt signed by the addressee only, to the last known place of business, residence or abode within or without this state of such person for whom the same is intended.