Spain's Inigo Landaluze was saved from sanctions by laboratory irregularities after failing a drugs test following his 2005 Dauphine Libere victory.
Landaluze tested positive for excess amounts of testosterone
An appeal by cycling's governing body the UCI against the decision of the Spanish Cycling Federation (RFEC) to acquit the rider has been rejected.
The Court of Arbitration for Sport (CAS) said he had not been cleared but accepted mistakes were made in testing.
The same person wrongly dealt with both the A and B sample, said CAS.
"The panel has considered that the non-compliance with this standard constituted a procedural flaw serious enough to cause the invalidation of the anti-doping test," said CAS in a statement.
"Even though Inigo Landaluze benefited from this flawed procedure to be acquitted, the CAS decision does not constitute a declaration of his innocence."
Landaluze tested positive for the banned substance testosterone after winning the eight-day Classic race ahead of favourites such as Santiago Botero, Levi Leipheimer and Lance Armstrong.