Cal. Veh. Code § 2403.5
The commissioner, or a designated representative, may enter into reciprocal operational agreements with authorized representatives of the Oregon State Police, the Nevada Department of Motor Vehicles and Public Safety, and the Arizona Department of Public Safety to promote expeditious and effective law enforcement service to the public, and assistance between the members of the California Highway Patrol and those agencies, in areas adjacent to the borders of this state and each of the adjoining states pursuant to Section 830.39 of the Penal Code. The reciprocal operational agreement shall be in writing and may cover the reciprocal exchange of law enforcement services, resources, facilities, and any other necessary and proper matters between the Department of the California Highway Patrol and the respective agency. Any agreement shall specify the involved departments, divisions, or units of the agencies, the duration and purpose of the agreement, the responsibility for damages, the method of financing any joint or cooperative undertaking, and the methods to be employed to terminate an agreement. The commissioner may establish operational procedures in implementation of any reciprocal operational agreement that are necessary to achieve the purposes of the agreement.
Ca. Veh. Code § 2403.5