The EU's top court said on Friday some international football rules regarding the transfers of players are contrary to the bloc's laws, in a landmark decision that could shake up the system.

The Court of Justice of the European Union (CJEU) was called on to decide a long-running dispute between former French footballer Lassana Diarra, once of Chelsea and Real Madrid, and world governing body FIFA over what happens when players unilaterally terminate their contract.

In a highly anticipated verdict, judges found that by restricting a footballer's ability to seek further employment, current FIFA rules hinder the EU's free movement and competition between clubs.

"The Court holds that all of those rules are contrary to EU law," it said.

The ruling could have far-reaching implications for the transfer market, allowing players to leave their club without fear of being legally trapped afterwards.

Diarra's Belgian lawyer Jean-Louis Dupont, who had dubbed the case "the Bosman 2.0 affair", hailed the new ruling as "a total victory".

Dupont was also involved in the landmark 1995 case of the then little-known player Jean-Marc Bosman, which allowed players to move to another club at the end of their contract without a transfer fee being paid and also ended quotas on foreign players at clubs.

In response to Friday's verdict, FIFA said it would "analyse the decision in coordination with other stakeholders before commenting further".

"FIFA is satisfied that the legality of key principles of the transfer system have been re-confirmed in today's ruling," it added.

"The ruling only puts in question two paragraphs of two articles of the FIFA Regulations on the Status and Transfer of Players, which the national court is now invited to consider."

But global players' union FIFPRO called the judgement "a major ruling". (AFP)