The Court of Justice of the European Union has ruled that certain international football regulations concerning player transfers are in violation of EU law, in a landmark decision that could disrupt the existing transfer system.

The court was called upon to resolve a long-standing dispute between former French footballer Lassana Diarra, who played for clubs including Chelsea and Real Madrid, and FIFA over the consequences of players unilaterally terminating their contracts.

In a highly anticipated verdict, the judges determined that current FIFA rules, by restricting a footballer’s ability to seek new employment, impede the European Union’s principles of free movement and competition between clubs.