Swiss sprinter Alex Wilson has been suspended from the Olympic Games after failing a drugs test, the Athletics Integrity Unit (AIU) said on Wednesday.
The 30-year-old Jamaica-born sprinter tested positive for the banned steroid trenbolone in an out-of-competition test on March 15.
Wilson had initially challenged the test result, arguing that the drug was contained in contaminated beef he ate at a Jamaican restaurant in the United States. He was provisionally suspended in March.
However a Swiss Olympic disciplinary panel lifted his suspension in early July.
The World Anti-Doping Agency and Athletics Integrity Unit appealed that decision to the Court of Arbitration for Sport, which on Wednesday upheld the initial suspension.
"Today's ruling is the right outcome and demonstrates a proper application of the rules," said AIU chief Brett Clothier.
"This case reflects the AIU's commitment to protecting the interests of clean athletes and ensuring a level-playing field in Tokyo."
Wilson made headlines on July 18 after appearing to clock a blistering 9.84sec for the 100m at a meeting in the United States, but the time has not been ratified amid doubts about its veracity.