The powerful European Club Association hailed the latest setback to the European Super League as "a clear rejection" of the plans of a "self-interested few".

UEFA and FIFA would be acting lawfully by freezing out the proposed competition and its teams, the European Union Court of Justice advocate general Athanasios Rantos said on Thursday.

Formally announcing his non-binding opinion in Luxembourg, ahead of a judgement expected in the new year, Rantos was responding to a request by a Madrid court for a ruling on whether FIFA and UEFA would have the right to take action in accordance with competition law and fundamental freedoms.

European Super League (ESLC) officials have argued such actions should be regarded as anti-competitive and incompatible with EU competition law.

Responding to the opinion from Rantos, the European Club Association (ECA) said the message proposed "a clear rejection of the efforts of a few to undermine the foundations and historical heritage of European football for the many".

Real Madrid, Barcelona and Juventus are no longer members of the ECA, having quit when the breakaway was announced in April 2021 and retained an interest in the breakaway getting off the ground even after its dramatic near-immediate collapse.

The nine clubs that fled the Super League project have returned to the ECA fold after withdrawing their resignations from the group. Those clubs are Chelsea, Arsenal, Liverpool, Manchester United, Manchester City, Tottenham, Atletico Madrid, Inter and Milan.

The ECA, which represents nearly 250 clubs, said it remained "explicit in its strong opposition towards those self-interested few seeking to disrupt European club football and undermine the values that underpin it".

In a statement, it added: "ECA stands for the responsible, progressive evolution of football and remains steadfast in its belief that in Europe this should be achieved alongside and in partnership with UEFA as the legitimate governing body, together with other fellow professional football stakeholders and European and governmental institutions.

"A great amount of positive reform and progress has been achieved by ECA working in collaborative partnership with UEFA in recent years for the benefit of the entire European football ecosystem."

FIFA also said it welcomed the news from Luxembourg. It backed the opinion that any new competition would need approval from the world and European governing bodies, and that sanctions could be imposed if that was not forthcoming.

FIFA praised the noting by Rantos "of the special nature of sport, including the pyramid structure, which preserves the nature of sporting merit and open competitions accessible to all, as well as the principles of promotion and relegation, competitive balance, and financial solidarity".

Bernd Reichart, CEO of A22 Sports Management, the company formed to deliver the Super League project, believes it can still be realised.

Clubs from across Europe's top leagues would be targeted to be involved, with the concern of those in opposition being that it would weaken existing competitions.

Reichart said: "The opinion of the advocate general is one step in an ongoing case, and we are pleased with the recognition of the right of third parties to organise pan-European club competitions.

"The advocate general made clear that UEFA has a monopolistic position which comes with important responsibilities for enabling third parties to act freely in the market.

"However, we believe the 15 judges of the Grand Chamber who are entrusted with the responsibility to examine this case, will go substantially further and provide the opportunity for clubs to manage their own destiny in Europe."