English Premier League football club Chelsea have appealed to the Court of Arbitration for Sport against the ban on signing new players imposed on them by FIFA.
Chelsea have also asked for the transfer ban to be suspended until the result of the appeal is decided.
They were found guilty in September of inducing Gael Kakuta to break his contract with French club Racing Lens and banned from registering any new players until January 2011.
The punishment was handed out following a contractual dispute involving the transfer of reserve team player Kakuta from Lens in 2007.
The London club were furious at the decision, describing it as "extraordinarily arbitrary" and "totally disproportionate", and promising to mount the strongest possible appeal.
If CAS upholds the appeal, Chelsea could sign players in the January transfer window.