French rugby chief Bernard Laporte has been given a two-year suspended prison sentence and a 75,000 euro (£64,000) fine for corruption, nine months before the country hosts the World Cup.
Laporte - vice-chair of World Rugby as well as president of the French Rugby Federation - was also banned from holding rugby posts for two years.
That ban is suspended pending an expected appeal from Laporte's lawyer.
His future position with World Rugby is unclear following the verdict.
A statement from the global governing body said the executive committee would meet on Tuesday night "to determine the next steps in accordance with the integrity code". It added that a further update would come following the meeting.
French Sports Minister Amelie Oudea-Castera said the sentence was an "obstacle for Bernard Laporte to be able, as it stands, to continue his mission in good conditions" as federation president.
Oudea-Castera called for a "new democratic era to allow French rugby to rebound as quickly as possible and sufficiently healthy and solid, with a governance by the federation that will have the full confidence of the clubs".
According to French news agency AFP, the court ruled that Laporte had showed favouritism in choosing France's shirt sponsor.
In March 2017, Laporte awarded a 1.8m euro (£1.5m) shirt sponsor contract to close friend Mohed Altrad, the billionaire owner of Top 14 champions Montpellier.
Altrad was given an 18-month suspended sentence and 50,000 euro (£42,800) fine. Both men deny any wrongdoing and Altrad's lawyer said he would study the decision before deciding on whether to appeal.
In February 2017, Laporte signed a 180,000 euro (£154,000) deal with Altrad group for his image reproduction rights and prosecutors claim Laporte did not deliver the services paid for.
Altrad's logo still features on France's shirts, with Laporte, 58, negotiating a follow-up deal in 2018.
Laporte, who coached France to the 2003 and 2007 World Cup semi-finals, was also found guilty of intervening with disciplinary action against Altrad's club Montpellier. He was convicted of helping to reduce a fine against the club from 70,000 euros (£60,000) to 20,000 euros (£17,000).
In November, financial prosecutors searched the headquarters of France's 2023 Rugby World Cup organisers as part of a government inquiry into the management of the organising committee.
'Laporte's rugby future thrown into doubt' - analysis
BBC rugby union correspondent Chris Jones
Laporte is one of the most powerful men in world rugby and was set to be a prominent figure at next year's World Cup in France, but this verdict throws his future involvement in the sport into serious doubt.
His position as vice-chairman of World Rugby is now untenable, with the governing body adopting a new integrity code in May 2021, followed by the appointment of an independent ethics officer earlier this year.
However, the investigated matter is not connected to World Rugby or Rugby World Cup activities.