After the increasing recourse from members of the football community to the State courts and national arbitral tribunals or dispute resolution chambers, the Court of Arbitration for Sport (CAS), in its recent jurisprudence, was faced with the issue of res judicata in numerous cases. When appearing as an arbitral tribunal in a dispute, where a final decision of a national arbitral tribunal or a State court exists, the CAS is obliged to examine, ex officio, the existence of res judicata - a general principle, which precludes adjudicating disputes that have already been decided.