An inquiry into the Alligator Blood positive swab from the Magic Millions 3YO Guineas will be held behind closed doors by Racing Queensland stewards.
The media will be barred from Thursday's proceedings, where one of Australia's top gallopers is facing disqualification.
A post-race swab detected traces of the prohibited substance altrenogest after Alligator Blood won the $2 million race on January 11.
Altrenogest, more commonly known as Regu-mate, is banned for use on male horses.
It is a hormone given to keep female horses from being in season, or if they are already pregnant, to keep them from losing the foal.
Alligator Blood's trainer David Vandyke was informed in March of the irregularity and it has taken until July for a hearing to be set.
Several media outlets sought to cover the case but stewards declined the requests.
In Queensland the stewards determine whether the media is allowed access to inquiries and there have been several instances where they have been held behind closed doors.
It is understood coronavirus restrictions were a factor in the decision.
Vandyke has been charged with presenting a horse to race with a prohibited substance, not the more serious administrating charge.
If found guilty Vandyke likely faces a fine, but Alligator Blood would be disqualified and the $1.2 million first prize would be forfeited.
Alligator Blood has won two races since the Magic Millions Guineas, including the Group One Australian Guineas at Flemington in February.
Both post-race swabs were clear.