The World Bridge Federation says the world's number one player has been suspended after failing a drug test.
It said Geir Helgemo, who is Norwegian but represents Monaco in bridge events, tested positive for two banned drugs at a world series event in Florida last September.
Mr Helgemo's tests showed he had taken synthetic testosterone and a female fertility drug, clomifene.
After accepting he had breached anti-doping rules, Mr Helgemo was suspended by the WBF until November 20. He also had all titles, medals and points from the 2018 World Bridge Series revoked.
Kari-Anne Opsal, president of the Norwegian Bridge Federation, said the drugs were "not performance enhancing".
In a statement on the federation's website, she said: "Geir Helgemo … has previously played for the Norwegian national team and is our biggest star. Many within the bridge community know Geir and respect him.
"It is his responsibility not to take substances that are on the doping list, even though in this instance they are not performance enhancing in bridge," she said.
"I feel for Geir in this situation and hope he will come back stronger … when his ban ends."
The World Bridge Federation is recognised by the International Olympic Committee and abides by World Anti-Doping Agency rules.