The FEI fined Mr Macken CHF3,000 (£1,776) for a “minor technical violation” of the rules at the Dublin Horse Show in August last year.
The 59-year-old rider is also disqualified from his placings at the event, which means Ireland lost its second place in the Aga Khan Trophy 2008.
Mr Macken, now based in Canada, failed to file a medication form for treatment his horse Tedechine Sept received for colic before the event.
As a result, the ground jury requested that the horse be dope-tested during the show.
Mr Macken signed an agreement on 6 August 2008 not to remove the horse from the show ground without the ground jury’s permission.
But, he claims, no one called the horse for testing before he left on the Sunday.
The FEI says Tedechine Sept could not be found on that day and that Mr Macken evaded having the horse tested.
But Mr Macken says he was available — and even received an award in the main arena.
On 27 August, the FEI tribunal cleared Mr Macken of “refusing or failing to submit a sample”, but ruled he was negligent in not seeking permission to leave the show ground.
“He agreed [to this condition] after being granted special dispensation to compete,” said the tribunal chairman Ken Lalo.
But Mr Macken told H&H: “I’m quite confused. There has been nothing fair about the way the FEI has treated me.”
Horse Sport Ireland declined to comment.
This article was first published in Horse & Hound (17 September, ’09)