Contador blamed steak bought from a Basque producer for his high reading of clenbuterol, which is sometimes used by farmers to fatten their livestock. To avoid a doping ban, he needed to prove how the anabolic drug entered his body and convince the panel he was not to blame.
In its ruling, CAS said the presence of clenbuterol was more likely caused by contaminated food supplement than by eating contaminated meat.
"Unlike certain other countries, notably outside Europe, Spain is not known to have a contamination problem with clenbuterol in meat," CAS said in its ruling in Lausanne, Switzerland. "Furthermore, no other cases of athletes having tested positive to clenbuterol allegedly in connection with the consumption of Spanish meat are known."
Contador is one of only five cyclists to win the three Grand Tours — the Tour, the Giro and the Vuelta. He also won the Tour de France in 2007 and 2009.
He becomes only the second Tour de France champion to be disqualified and stripped of victory for doping. The first was American Floyd Landis, who lost his 2006 title after testing positive for testosterone.
"There is no reason to be happy now," Schleck said in a statement issued by his team, RadioShack Nissan Trek. "First of all I feel sad for Alberto. I always believed in his innocence. I battled with Contador in that race and I lost."