Toulon could take legal action against the Leicester fans whose testimony led to the 12-week suspension of Trinidad-born England outside centre rugby player Delon Armitage.
The 31-year-old San Fernando-born Armitage, was punished for using offensive language towards spectators after a European Rugby Champions Cup match at Welford Road on December 7.
Toulon president Mourad Boudjellal told newspaper La Provence that there was "no formal proof" against Armitage.
"We aren't discounting the eventuality of going after these two supporters in court for false testimonies," he said.
He added that the ruling against Armitage was "incomprehensible."
"This is an extraordinary decision which rests only on the allegations of two opposition supporters, whose objectivity we can legitimately put in doubt," said Boudjellal.
"But there is no formal proof, no official document, not even television pictures to attest to the veracity of these testimonies."
English full-back Armitage will be suspended until March 8. It was his second post-match misconduct case in the last four years.
On Wednesday he pleaded not guilty at a misconduct hearing on Wednesday, but a disciplinary committee ruled he had "conducted himself in an unsportsmanlike manner," despite accepting he was "provoked."
The incident occurred just before team-mate Martin Castrogiovanni launched into a post-match rant to journalists about Leicester director of rugby Richard Cockerill.
Castrogiovanni was fined �10,000 (�8,000) fine and given a suspended four-game ban.
The committee said Armitage "may have brought into disrepute" the sport by "making a number of comments to, or within earshot of, spectators using foul and abusive language."
However, it cleared him of one comment allegedly made during the game at Welford Road on� December 7 because "inconsistencies in the evidence were too great."
Armitage's ban was increased from a starting point of eight weeks to 12 because it was his second post-match misconduct case in four years.
He pushed an anti-doping officer during a drugs test after playing for London Irish against Bath on 1 January 2011.
His brother, 29-year-old Steffon Armitage who was also born in San Fernando, Trinidad) is a rugby union player for RC Toulon in the Top 14 and has represented England five times since making his debut in 2009.
Before moving to Toulon in 2011, Steffon, a flanker, previously played at Saracens (2004-2006) and London Irish (2006-20011) while he represented Richmond and Racing Rugby Club de Nice, just as his older sibling.
Armitage's stepfather John played rugby for Hatfield and encouraged his sons to such an extent that four of them are now professional players. Guy plays at Irish. Steffon is also a member of the Saxons squad and Toulon. Bevon left RFU Championship club Doncaster Knights in 2010 for his brothers' youth club Rugby Nice C�te d'Azur Universit�-Racing.
He is back a Doncaster from the 2013-14 season and is the first native West Indian to play rugby union for England.