An unnamed Russian player was stopped by Czech police from entering the country to compete in the WTA Prague Open.
A new government resolution has banned athletes from Russia or Belarus taking part in any events in the Czech Republic.
Several Russian and Belarusian players had been expected to compete in Prague as neutrals.
But tournament organisers have now told them not to travel.
Tournament director Miroslav Maly said: "She was the first participant to arrive to the Czech Republic with a Russian passport.
"The management of the tournament fully respect the current stance of state authorities.