Yoann Maestri has been fined £26,000 for comments he made about the referee after France's Six Nations game against Wales.
The Toulouse lock accepted a misconduct charge over the remarks, made to French media about Wayne Barnes after his side won a chaotic final game 20-18.
Half the fine is payable within 30 days, while the other half is suspended until the end of next season.
A statement from tournament organisers, released after a hearing on Wednesday, said Maestri "accepted he had committed an act of misconduct and openly apologised for making the comments."
The statement added: "The disciplinary committee also ordered Mr Maestri to pay Six Nations' legal costs. Both parties were reminded of their right of appeal."
France scored 20 minutes into added time to win the Paris meeting, and Wales' interim head coach Rob Howley was later critical of the home side's conduct.