The Belgian, who has been champion jockey in France 10 times and has won major races all over the world, has had a controversial summer.
He first picked up a lengthy ban when winning the Eclipse at Sandown on Vadeni, allowing his mount to drift to his right shortly after the line in celebration, narrowly avoiding a major incident.
Then on Friday at Saint-Cloud Soumillon could be seen to move to his right mid-race in the Prix Thomas Bryon, sticking out an elbow, which forced Rossa Ryan on Ralph Beckett's Captain Wierzba to be unseated.
Soumillon was given a 60-day suspension by the France-Galop stewards but the fact the ban did not kick in immediately angered many and he was allowed to take his high-profile mounts on Arc weekend, and he went on to finish second in the big race itself on Vadeni.
Thankfully Ryan escaped injury in the incident.
A statement issued on social media by the Aga Khan Studs read: "Following last Friday's incident at Saint-Cloud, which resulted in the fall of Rossa Ryan, the Aga Khan Studs have taken the decision to cease their retainer with Christophe Soumillon with immediate effect.
"From this week onwards, Soumillon may still ride in the Aga Khan silks on occasion at the discretion of the French trainers and the Aga Khan Studs team.
"At this stage, there is no intention to retain a jockey in France for the foreseeable future.
"Christophe Soumillon was the Aga Khan's retained rider in France from 2002 to 2009 and from 2014 to 2022."