Nice have been prevented by FIFA from registering new signing Hatem Ben Arfa.
Ben Arfa, a free agent after his release from Newcastle, joined the club last Monday but was not available for Saturday's win over Lorient as he awaited international clearance.
The problem was due to the clause in FIFA's transfer regulations which states a player cannot play for more than two clubs in the same season.
Article 5.3 of FIFA's regulations on the status and transfer of players states: "Players may be registered with a maximum of three clubs during one season. During this period, the player is only eligible to play official matches for two clubs.''
Ben Arfa made eight appearances on loan at Hull -- and an appearance for Newcastle's under-21 side earlier in the season has been ruled by FIFA to be an "official" match.
A statement on Nice's official website read: "OGC Nice have received a copy of a correspondence sent by FIFA to the FFF (French Football Federation). The international federation responded to the question posed by the French federation regarding a match played by Hatem Ben Arfa with Newcastle Under-21s.
"Contrary to the position of the English (Football Association), it appears that for FIFA the match in the U21 Professional Development League 'must be considered as official in the sense of the regulation' and 'must therefore be taken into consideration in determining the application of article 5.3 of the regulation' on the status and transfer of players.''
Nice's statement came after a FIFA spokesperson told Press Association Sport: "Our services received an information request from the French Football Federation concerning the player Ben Arfa relating to art. 5 par. 3 of the regulations on the status and transfer of players. We can confirm that today we have responded to the FFF regarding their information request.''
The development leaves Ben Arfa, who has 13 France caps to his name, in limbo. Hull pulled the plug on his loan deal after he fell out of favour with manager Steve Bruce, and a Newcastle statement on Jan. 4 read: "Hatem Ben Arfa and the club have reached an agreement to terminate the contract between both parties with immediate effect by mutual consent.''
The match at the centre of the impasse was between Newcastle's U-21 side and their counterparts from Reading on August 25. Ben Arfa scored his side's fourth goal in a 5-2 win.
A previous statement from Nice on Monday expressed hope that "sporting logic'' would prevail and allow him to return to action in Ligue 1.
The statement read: "The return of the France international is not yet official from an administrative point of view due to a point raised by our federation (the FFF) with FIFA, despite a positive and unequivocal response from the English federation. The question raised by the FFF did not concern the first team but the match played in August by Hatem Ben Arfa, 27, with the Newcastle Under-21s.
"(The FA) confirmed in writing to the French federation, when asked, that it is not in any case an official match - information which legitimises the position of the club and which has been sent to FIFA as we await their decision.''
Coach Claude Puel was asked about the issue at his press conference earlier on Wednesday, at which stage he was confident the move would be ratified.
In comments published on the club's official website, Puel said: "For us, his eligibility is not in doubt. The English federation wrote to the French federation and to FIFA explaining that the match played by Hatem (for Newcastle) did not count towards an official competition. We are optimistic and positive that he can return to France, return to Ligue 1 and, I hope, explode with OGC Nice.''
Puel had hoped to be able to include Ben Arfa in his squad for this Friday's Ligue 1 clash with Bordeaux, but added: "As a coach, you have to adapt to any situation. The team showed against Lorient that they are capable, even without Hatem.''