Jockey Stephane Pasquier has had a three-month riding ban suspended at a civil court tribunal in France, said his agent Nerve Naggar.
Pasquier is free to ride from Thursday after "a serious doubt about the legality of the ban" emerged during the tribunal.
The stewards of racing authority France Galop issued the ban after Pasquier tested positive for a prohibited substance at Longchamp on April 11.
His suspension began on August 14, but Pasquier can now feature at Longchamp's Arc Trials fixture on Sunday.
"This is historical news and has never been known before. He has got back his licence and he is free to ride from tomorrow," Naggar said.
"He will ride at Fontainebleau on Saturday and will then ride on Arc Trials day at Longchamp, where he will ride Maxios.
"The emergency court decided to suspend the ban immediately because they considered there was a serious doubt about the legality of the ban.
"It will now be treated in the courts next year, so this is a big step forward.
Pasquier, 35, won the 2006 Prix de l'Arc de Triomphe aboard Rail Link and was successful in the 1000 Guineas at Newmarket three years ago when Special Duty was awarded the race in the stewards' room.