Ukraine's Olha Kharlan was disqualified for not shaking the hand of her beaten Russian opponent Anna Smirnova at the Fencing World Championships on Thursday.
Four-time sabre world champion Kharlan had told AFP a fortnight ago she would not shake hands with a Russian if she fought one.
She had earlier become the first athlete officially representing Ukraine to face a Russian or Belarusian opponent since Russia invaded Ukraine in February 2022.
The 32-year-old had been given the green light only at 0600GMT on Thursday morning, coming hours after the Ukraine sports ministry late Wednesday changed its previous policy of barring athletes from facing Russians or Belarusians competing as neutrals.
The new policy says Ukrainians cannot face athletes who "represent the Russian Federation and Belarus".
Smirnova was competing as a neutral.
Ukrainian tennis players have been playing Russians and Belarusians since the invasion, but as individuals not representing their country.
They too have avoided shaking hands with their opponents.
"They are right not to shake hands, I cannot imagine a scenario where I would," Kharlan told AFP.
"We have different fronts, we also have sport which is about the fight and the struggle."