Turan joined the reigning La Liga champions on a five-year deal from Atletico Madrid over the summer but will have to wait until January to play for his new team under the current ruling.
Barcelona are serving a transfer ban and will be able to register new players next year however, the Spanish Football Federation (RFEF) has a special clause that allows clubs to replace players out with long-term injuries with an unregistered players.
The Champions League titles holders have been permitted to unregister Rafinha who is out injured for the foreseeable future with Turan by the RFEF however, FIFA have warned that the move could conflict with their rules.
Barcelona have urged FIFA to clarify their stance. If the world football governing body does not block the registration the La Liga giants could have Turan playing for them after the international break. Alternatively if FIFA do block the process Barcelona will hope for a CAS decision by the end of November.