Marco Kutscher and Cornet Obolensky. © Luca di Stefano/FEI
Kutscher rode the horse in the showjumping competition at the Hong Kong venue in the Beijing Games.
Kutscher admitted to the tribunal that the horse had been treated with Lactanase, a medication prohibited at the games.
However, he said believed at the time that the team veterinarian had followed the necessary protocols to ensure the treatment was permitted and within the rules.
The panel found Kutscher had violated the anti-doping and medication rules with the undocumented treatment.
As a consequence, Kutscher and the horse have been disqualified from all placings at the 2008 Games.
Kutcher did not claim any medals at Beijing, but did win two bronzes at the Athens Olympics in 2004.
A suspension was not imposed as the tribunal felt the timing would be unfair, but he was instead fined an unprecedented 10,000 Swiss francs ($US8840) because of his negligence and ordered to pay 5000 Swiss francs towards the costs of the proceedings.
Kutscher has 30 days to appeal the decision to the Court of Arbitration for Sport.