Last week the sport's governing body FISA ruled that six Russians were eligible for the Games but banned 17, plus two coxes, after ruling that they did not meet the IOC's new criteria of being regularly drug-tested outside Russia.
They had already previously banned three rowers who had served doping bans or who had been named in the McLaren report for WADA that exposed Russia's "disappearing positives" regime.
The rowers, along with several other Russian athletes from other sports, had their appeals heard by CAS on Tuesday (local time) and Inside the Games reported that the Court upheld the principle of athletes being ruled ineligible if they cannot effectively "prove they are clean."
The bans have caused some last-minute reshuffling of the Rio rowing programme, after FISA said the six eligible Russian athletes could form one four-man crew.
Russia's lightweight men's four, men's and women's eight and lightweight women's double boats, have all been removed from the competition as a result of the decision of the FISA Executive Committee.
Greece are set to take the spot of the men's four, while the place of the men's eight has been given to Italy, who have also been handed Russia's berth in the women's lightweight double. Australia have been offered the slot in the women's eight.
