The former world cycling champion Tom Boonen faces a suspension of up to six months after failing an out-of-competition test for cocaine.
It is the Belgian's second offence in 12 months after he also tested positive for the same substance in an out-of-competition control last year.
When the Quick Step rider's latest positive test was announced on Saturday the UCI said Boonen would not be punished by the governing body "since the use of cocaine out of competition is not subject to sanctions".
However, the UCI said today the behaviour of Tom Boonen, even though it does not constitute a violation of the anti-doping rules, can be considered unacceptable and liable to harm the image, reputation or interests of cycling or the UCI.
The UCI says this infringement is punishable by a suspension of one to six months.
Boonen, who won the road world championships in 2005, was targeting the green jersey for the best sprinter in this year's Tour de France which starts on July 4th in Monaco.
He has already been suspended by his team for "an unspecified period of time".