California Code, Business and Professions Code - BPC § 19455.4

The board may establish reasonable rules to regulate the time, place, and manner for representatives of labor unions to meet backstretch workers within the enclosure during working and nonworking hours.  Those rules shall provide that the union and its representatives shall not interfere with the work of any employee, but shall have reasonable access to backstretch employees within the enclosure during working hours and nonworking hours, as determined by the board.  With the approval of the board, these regulations may be superseded by collective bargaining agreements between horsemen's organizations or trainers' organizations and labor organizations.