National courts must be allowed to conduct in-depth reviews of arbitral awards by the Court of Arbitration for Sport (CAS) to ensure they are compliant with EU law, the European Court of Justice said on Friday.

The ruling comes after RFC Seraing were banned from registering new players and also fined by soccer's governing body FIFA in 2015 when the Belgian club signed agreements with a company that transferred part of the economic rights to players.

FIFA ruled their deal with a Maltese company Doyen Sports as a breach because third parties are not allowed to hold economic rights to players, with the sanctions being upheld by the CAS - sport's top court - as well as the Swiss Federal Supreme Court.

However, Seraing brought the case before Belgian courts to challenge the compatibility of FIFA's rules with EU law.

Although CAS awards are considered final and cannot be relitigated, the Belgian court approached the Court of Justice, which said such a scope is contrary to EU law.

"It is essential that recourse to arbitration does not undermine the rights and freedoms that the fundamental rules of EU law guarantee athletes, clubs and, more broadly, any other person practising a professional sport or pursuing an economic activity linked to that sport," it said.

"On those grounds, the Court of Justice rules today that the national courts or tribunals must be empowered to carry out... an in-depth judicial review as to whether arbitral awards made by the Court of Arbitration for Sport (the CAS) are consistent with EU public policy."

The Court of Justice found that in Seraing's case, FIFA made the club go to CAS to settle the dispute, rather than letting the club choose how to resolve it - a setup common in resolving sports-related disputes.

"The Court rules that, in order to ensure effective judicial protection for athletes, clubs and other individuals who might be affected as a result of pursuing a sports-related economic activity within the European Union, the awards made by the CAS must be amenable to effective judicial review," it added.

The ruling effectively undermines the absolute finality of CAS decisions, especially when such decisions are based on arbitration clauses imposed unilaterally by sports bodies.

The Court of Justice also said that any country's laws that treat such CAS awards as immune from further scrutiny are incompatible with EU law.

"The Court adds that a national court or tribunal is required to disapply of its own motion any national legislation or rules of a sports association that would hinder such effective judicial protection as regards individuals," it said.

Reuters has contacted FIFA and the CAS for comment. REUTERS