Cal. PUC § 5363

(a) Any provision of the Public Utilities Act (Part 1 (commencing with Section 201) of Division 1) or of this chapter applicable to charter bus transportation that conflicts with the federal Transportation Equity Act for the 21st Century (P.L. 105-178) does not apply to charter bus transportation to the extent of that conflict. If any provision of the Public Utilities Act or of this chapter applicable to charter bus transportation, or the application thereof to any person or circumstance, is invalid as a result of federal preemption, the remainder of the act, or the application of the provision to other persons or circumstances, shall not be affected thereby.

(b) (1) Except as specified in paragraph (2), as used in this section, “charter bus transportation” means transportation, using a vehicle designed, used, or maintained for carrying more than 10 persons, including the driver, of a group of persons who, pursuant to a common purpose, under a single contract, at a fixed charge for the motor vehicle, have acquired the exclusive use of the motor vehicle to travel together.

(2) If a federal court or agency with the jurisdiction to construe Section 14501(a)(1)(C) of Title 49 of the United States Code determines that additional transportation falls within the meaning of the term “charter bus transportation,” as used in that section, the federal construction of that term shall prevail.