The controversy surrounding the case has resulted in Chelsea being dealt a transfer embargo up to 2011.
“We sat with them (Chelsea) and told them the player was under contract but they argued that he was not,” Didier Roudet, Lens’ general secretary, said in the Daily Mail.
“All I can say is that our lawyers are very confident of their position and so are Fifa.
“Lens are a little team. Chelsea are a big team with a lot of money and, for sure, the player’s family were offered a lot of money. We could not keep the player.”