California Code, Business and Professions Code - BPC § 7521.5

(a) A private investigator may provide services to protect a person, but not property, which is incidental to an investigation for which the private investigator has been previously hired to perform.

(b) If the private investigator provides those services, he or she shall comply with the requirements of Article 4 (commencing with Section 7540), as those provisions relate to the carrying of firearms and the receipt of a valid firearms qualification card from the bureau.

(c) If the private investigator provides those services, he or she shall comply with the requirements of Sections 7583.39, 7583.40, and 7583.41, as those provisions relate to the maintenance of an insurance policy.

(d) If a person acts for, or on behalf of a private investigator in providing those services, that person shall be an employee of the private investigator, as defined by Section 7512.11, and there shall be an employer-employee relationship, as defined in Section 7512.12, and that person shall comply with the requirements of this section, except as provided in subdivisions (b) and (c).