California Code, Business and Professions Code - BPC § 6747

(a) This chapter, except for those provisions that apply to civil engineers and civil engineering, shall not apply to the performance of engineering work by a manufacturing, mining, public utility, research and development, or other industrial corporation, or by employees of that corporation, provided that work is in connection with, or incidental to, the products, systems, or services of that corporation or its affiliates.

(b) For purposes of this section, “employees” also includes consultants, temporary employees, contract employees, and those persons hired pursuant to third-party contracts.