FEI identified the athletes as Rio 2016 flag bearer and royal family member Sheikh Ali al-Thani and Bassem Mohammed, who both tested positive for Carboxy-THC, a metabolite of cannabis, which is a prohibited substance under the FEI's Anti-Doping Rules for Human Athletes (ADRHA).
The riders, however, have not been provisionally suspended, as Carboxy-THC is a 'Specified Substance' banned in competition under the 2019 World Anti-Doping Agency (WADA) Prohibited List. The FEI explained that a 'Specified Substance' is "more likely to have been consumed by an athlete for a purpose other than the enhancement of sport performance". "Positive cases involving Specified Substances can be handled with a greater degree of flexibility within the structure of the FEI regulations," it said. Al-Thani finished sixth in the individual event in Rio, while the Qatari jumping team came ninth.