A Barcelona member has filed complaints with a French court and the European Commission with the aim of blocking Lionel Messi's potential move to Paris St Germain, according to documents seen by Reuters on Monday.
In the complaints, shared by the fan's lawyer Juan Branco, the Barca member says French football authorities have failed to enforce financial fair play (FFP) rules in order to help PSG become a force in European football.
Barcelona, like their main La Liga rivals Real Madrid, are fully owned by their subscription-paying members known as "socios".
FFP rules forbid top European soccer clubs from paying their playing squads an excessive share of their total revenues, according to the member's complaints, which also state that the transfer of 34-year-old Argentine Messi to PSG would breach the code.
The EU executive confirmed receipt of the complaint.
"The Commission is assessing the complaint under its standard procedures," a spokesperson said.
PSG and France's professional soccer league LFP did not immediately respond to requests for comment.
Sam Boor, a senior manager in Deloitte's sports business group, told Reuters in April that European soccer's governing body UEFA has historically said a 70% wage-to-revenue ratio should be the upper limit for clubs to target. But he added that a number of large clubs may go past that figure and possibly even breach 100% in the short term.
Any transfer of Messi from Barcelona to PSG would constitute a distortion of competition with other national leagues, the complaints say, and would be detrimental to Barcelona fans.
This distortion would affect soccer market competition within the European Union, according to the complaint filed with the EU's executive body, and thus constitutes unlawful state aid.
The Commission can order EU governments to claw back state aid if it is found to have given companies an unfair advantage.