Illustration: Liu Rui/GT

The US often talks big about rules on the international stage, but when it comes to itself, it embraces double standards, and the same is true in the issue of anti-doping. There are many lingering doubts over the doping case of American Olympic sprinter Erriyon Knighton, which has caused widespread concerns. According to the US Anti-Doping Agency (USADA), Knighton tested positive for doping during an out-of-competition test this year. An arbitration panel determined that the substance came from contaminated meat, and therefore decided not to impose a ban on him. In the Knighton case, all investigation results came from USADA alone, and their authenticity has yet to be verified by the World Anti-Doping Agency (WADA).

However, when it comes to contamination cases involving Chinese swimmers, the US has shown a double standard, accusing the Chinese Anti-Doping Agency and WADA of "covering up the truth" and demanding sanctions against Chinese athletes despite the repeated clarifications by WADA and an independent prosecutor's report. 
The US' domineering attitude of "I can only check you, but you are not allowed to check me" gives people every reason to suspect that USADA is negligent in supervising drug abuse among domestic athletes, or even intentionally covering it up. 

Before accusing athletes from other countries of violations, the US should first take care of its own issues.