If in the opinion of the judges or the starter a horse is unmanageable or liable to cause accidents or injury to any other horse or to any driver, it may be sent to the barn. When this action is taken, the starter will notify the judges who will in turn notify the public.
58 Pa. Code § 183.235
This section cited in 58 Pa. Code § 183.236 (relating to placing bad acting horses on outside positions).