The decision from the Court of Arbitration for Sport in Lausanne, Switzerland, which overturns an earlier ruling by the Spanish cycling federation, means Contador will be banned from racing for two years.

Contador stopped racing between August 2010, when the positive test was announced, and last February, when the Spanish federation issued its decision. Thus, the suspension will end Aug. 5, shortly after this year’s Tour de France.

The panel also ordered that Contador, 29, of Spain, be stripped of his 2010 Tour title, which would go to the second-place finisher, Andy Schleck of Luxembourg. He will also lose all of his results from last season, including a second victory in the Giro d’Italia.

On the last rest day of the 2010 Tour, Contador tested positive for clenbuterol, a weight-loss and muscle-building drug that some riders illicitly use during the offseason to improve their performance on big climbs in the mountains. Contador said it came from tainted steaks that a friend had delivered from Spain to France.

He also tested positive for a category of chemicals known as plasticizers, which are found in some IV bags used to store blood. While it was not part of the current investigation, the presence of plasticizers suggested that Contador also engaged in blood doping.

The decision was another setback for a sport that has repeatedly had its top athletes become tangled in doping scandals. Since 1995, only two Tour de France winners - Carlos Sastre in 2008 and Cadel Evans last year - have not been tarnished by controversies involving performance-enhancing drugs.

On Friday, federal investigators announced that they had ended a criminal investigation of Lance Armstrong, who won the Tour from 1999 to 2005. The US Anti-Doping Agency, with the support of the World Anti-Doping Agency, is continuing a separate investigation of Armstrong under its rules.

“This is a sad day for our sport,’’ said Pat McQuaid, the president of the International Cycling Union which, along with the World Anti-Doping Agency, had appealed the Spanish decision clearing Contador.

“Some may think of it as a victory but that is not at all the case. There are no winners when it comes to the issue of doping: Every case, irrespective of its characteristics, is always a case too many.’’

A spokesman for Contador’s team, Saxo Bank, said the decision was still being reviewed and declined to comment.

The amount of clenbuterol found in Contador’s blood was low, but any amount is deemed to be a violation of anti-doping rules.

Contador was unable to provide samples of the beef that he said was purchased in Irun, near the French border, and delivered to his team’s hotel in Pau. So the case became a battle of experts who offered conflicting evidence about the plausibility of his claim.

In January 2011, the Spanish cycling federation proposed that Contador should receive a one-year suspension from racing, rather than the two-year penalty that is customary for first offenses. But the next month, it changed course and cleared him.

In its decision yesterday, the tribunal concluded that neither blood transfusions - the World Anti-Doping Agency’s theory - nor Contador’s contaminated meat defense were the likely cause of the positive test. It concluded that food supplements which Contador consumed in great quantities were likely to blame.

The International Cycling Union, known by its French initials UCI, and the World Anti-Doping Agency appealed to the Court of Arbitration for Sport.