Bailey, who is 28, was fifth in the 100m at London in 2012 and ran the anchor leg for the 4x100 relay team, which finished second but was stripped of its medals after Tyson Gay failed a drugs test.
Bailey switched to bobsleigh in 2016 with an eye on the Olympics in Pyeongchang, South Korea, in January and February.
In January 2017, he raced in the two and four-man bob in the North American Cup in Park City, Utah. He was tested after winning the two-man race and the sample showed traces of dimethylbutylamine, a banned stimulant.
The United States Anti-Doping Agency appealed for a heavier punishment. CAS heard the case in Los Angeles on November 29 and on Friday announced a ban starting on November 30. CAS made clear that the time Bailey has already served would be deducted from the ban, but the ruling still means he cannot compete in the Olympics.