Frankie Dettori's solicitor Christopher Stewart-Moore has claimed that the Italian jockey is not guilty of taking a performance-enhancing drug.
The former National Hunt jockey is facing an investigation by the French authorities after testing positive to a banned substance from a race in France this September.
"There are a large variety of substances which are banned by France Galop," BBC Sport quotes Stewart-Moore as saying.
"We are not going to say which substance he has tested positive for as that would be in breach of their rules, but it's not a performance-enhancing drug."
Dettori could be banned from racing for six months.