Cycling South Africa reports that Tyronne White has been found guilty of an anti-doping rule violation after an in-competition test conducted on 30 April 2016 confirmed the presence of the Glucocorticoid, Dexamethasone.
The SAIDS Independent Doping Hearing Panel imposed a period of ineligibility of 18 months, commencing on 14 December 2016. Mr. White is therefore suspended and prohibited from competing and administering in the sport of Cycling as well as in any other sport in South Africa and Internationally from 14 December 2016 until 13 June 2018. This decision may be appealed by Mr. White, the UCI, WADA and SAIDS.
Cycling South Africa respects the independence of the SAIDS process and will respect the outcome. Cycling SA further reiterates its zero-tolerance approach to doping in sport and will continue working with SAIDS in the promotion of a drug-free sport via its awareness and extensive testing programmes.

I suspect they also have some more control during the CE but it will be a difficult call - doctors are not policemen and you might for instance let a patient go back to their accomodation overnight for instance with an instruction to return in the am for further assessment... what happens if they don't come back and carry on? I am pretty sure it can be done but there would have to be clear clinical criteria set and rules in place - not going to be easy at all.