Racing Victoria has won a long-running battle against horse trainer Mark Riley after it successfully appealed a decision that cleared him of a doping charge.

Riley was slapped with a three-year racing ban after he was found to have administered a prohibited substance to his horse Gold For Kev following a race at Sandown Racecourse in July 2014.

Riley appealed the matter to VCAT and then the Victorian Supreme Court, submitting the rules of racing did not allow "rounding up" when testing for a prohibited substance.

Most of the 80 categories on the Australian Rules of Racing's prohibited substance list are banned absolutely, but some cease to be prohibited if they are present at or below specified levels.

Riley's case concerned "alkalinising agents", which are acceptable at or below levels of 36.0 millimoles per litre in plasma.

When a blood sample was taken from Gold For Kev in July 2014, testing revealed alkalinising agent levels of 37.061 millimoles per litre.

The lab rounded that up to 37.1 mmol/L, but noted a measurement uncertainty of 1.0 mmol/L.

Taking the uncertainty into account, the reading was treated as 36.1 mmol/L and the Racing Appeals and Disciplinary Board found Riley guilty of administering a prohibited substance and banned him for three years.

Riley said this was against the rules and was last year cleared by the Supreme Court.

Justice Kevin Bell found the rules did not permit a disqualification to be imposed on the basis of rounded-up results.

Racing Victoria filed an appeal and on Wednesday the Court of Appeal found in its favour.

Riley has been ordered to pay Racing Victoria's costs.