36-year-old Schwazer took the gold in the 50 km in Beijing in 2008 but was suspended in 2012 for almost four years for blood doping.
He was back in 2016 but was then suspended for eight years after leaving a doping test that contained traces of anabolic steroids.
An Italian court acquitted Schwazer of that verdict in February and he wanted the verdict lifted internationally as well.
Continued to train before the Olympics
Cas has rejected an urgent request for a provisional lifting of the sentence following a letter submitted by Alex Schwazer.
He demanded that Cas should decide that the eight-year sentence be overturned ", Cas writes in his verdict.
During the process, Schwazer has continued to train to be ready for the Olympics.
He has now turned to the Swiss Supreme Court, which, however, very rarely takes up Cas judgments.
- I want to end my career whenever I want, he said after the acquittal in February.