Frankie Dettori faces a France Galop inquiry tomorrow after testing positive for a banned substance at Longchamp in September.
His solicitor Christopher Stewart-Moore released a statement last week which said the jockey would appear before the medical committee of the French racing authority in Paris.
Dettori could face a six-month ban, which would be expected to be reciprocated by racing jurisdictions worldwide.
Stewart-Moore declined to name the substance involved, but said it was "not a performance-enhancing drug".
Dettori had four rides at Longchamp on September 16, a day of major trials for the Prix de l'Arc de Triomphe meeting the following month.
France Galop have not commented on proceedings and, in previous similar cases, have not issued a statement before the hearing.
Dettori made the headlines last month when his 18-year association with powerful owners Godolphin came to an end, with the three-times champion jockey planning to ride as a freelance in 2013.
A number of bookmakers have now, however, removed Dettori from their betting for next year's jockeys' championship.
Kieren Fallon was banned for six months by France Galop in 2006 after returning a positive test for a metabolite of a banned substance.
France Galop then banned him a further 18 months after a second positive test in August 2007.
Dettori himself was cautioned by police for possession of cocaine in 1993.
Asked by the Daily Mail in 2010 about his biggest regret, he said: "Getting caught with cocaine in 1993.
"I was on all the front pages and put my family through hell.
"I was cocky and had too much too soon.
"It made me grow up."