Cal. Public Utilities Code § 5355.5

(a) “Chartering party” means the person, corporation, or other entity that prearranges with a charter-party carrier of passengers for transportation services. (b) “Designee” means a person who is 25 years of age or older and who is designated by the chartering party as being the person responsible for compliance with the requirements of Section 5384.1 during the provision of transportation services whenever persons under 21 years of age are to be transported unaccompanied by a parent or legal guardian. If the chartering party is a person and the minor is not accompanied by a parent or legal guardian, the chartering party shall be the designee unless the chartering party identifies another person to be the designee and the person so designated acknowledges and agrees that he or she is the designee. If there is more than one chartering party for a joint carriage of passengers, each chartering party shall designate a designee who is responsible for compliance with the requirements of Section 5384.1 whenever persons under 21 years of age are to be transported unaccompanied by a parent or legal guardian, and that person shall be the designee only for those passengers provided with transportation services on behalf of that chartering party.