Here is the actual rule. You'd think the RIB could at least transpose it correctly.
656 (1) A Rider who rides or presents himself to ride a horse, or any other Licenceholder who has carried out, is carrying out, or is likely to carry out, a Safety Sensitive Activity at a Racecourse, Training Facility or Trainer’s Premises shall thereby be deemed to have consented to a Sample being obtained from him by or under the supervision of a Registered Medical Practitioner or by an Authorised Person if and whenever the Rider is required by a Stipendiary Steward or Investigator to permit such a Sample to be so obtained. [Amended 1 December 2013] [Amended 1 August 2014]