French jockey Christophe Lemaire has been banned by the Japan Racing Association (JRA) for using Twitter during a race meet.
The Melbourne Cup winner had been due to make his debut as a fully-licensed jockey at the Hashin racecourse in Japan.
JRA rules prohibit jockeys from contacting anyone until after their final race during the meet.
Lemaire had retweeted an acquaintance's post and was banned until 31 March.
Stewards at the racecourse found the 35-year-old - who was returning after three months out with a broken leg - had not switched off his phone on the Saturday evening, after checking in to the jockey's quarter the day before the race.
The Japan Racing Association's Paris representative Fumi Tsuruoka said: "It is prohibited for the jockeys to contact any person outside after checking in the jockey's quarter until when he/she finishes his/her final ride in that race meeting for the purpose of integrity."
Lemaire has no right to appeal under JRA rules and was banned from 1 March to 30 March inclusive.