Lausanne's Court of Arbitration for Sport (CAS) on Monday upheld FIFA's one-year transfer embargo imposed on newly promoted French Ligue 1 side Nantes, due to a dispute over the signing of Guinea's Ismael Bangoura in January 2012.
Nantes were accused of having incited Bangoura to unilaterally break his contract with Dubai's AL Nasr prematurely, before signing for the French club in January 2012.
In February, FIFA ordered Nantes, and Bangoura, to pay Al Nasr 4.5 million euros ($5.8m) in damages while the striker was suspended for four months, the remainder of the current season.
All three parties appealed the decision, Al Nasr because they felt the sum was too low.
But on Monday CAS threw out the appeals from all three parties.
In a statement CAS said: "The three appeals have been dismissed and the decision of the FIFA Dispute Resolution Chamber has been confirmed in its entirety. Therefore, amongst others, FC Nantes remains banned from registering any new players for the next two transfer windows."
Nantes general manager Franck Kita told AFP the club would appeal.
However, whereas the club was allowed to sign players during the appeal period between FIFA's original decision and the CAS ruling, this time the transfer embargo has not been momentarily suspended.
It means Nantes will not be able to bring in any new players before beginning next season in Ligue 1.
They will not be allowed to sign players during the January 2014 transfer window either.