Atletico Madrid have demanded La Liga prevent Antoine Griezmann from playing for Barcelona next season, according to the Spanish top flight's president Javier Tebas.
Griezmann confirmed he would be leaving Atleti at the end of last season, despite having only signed a five-year contract at Wanda Metropolitano in June 2018 after turning down a move to Barca.
After much speculation, Barca confirmed World Cup winner Griezmann's signing on July 12 after paying the France forward's €120 million (£107m/$134m) buy-out clause.
However, Atleti have reported Barca to The Royal Spanish Football Federation (RFEF), who have subsequently opened an investigation into the transfer.
Atleti claim they are owed a further €80 million, on top of the €120 million already paid for Griezmann, who made his Barca debut in a friendly defeat to Chelsea in Japan on Tuesday.
Griezmann's release clause originally stood at €200 million, but dropped to €120 million midway through this summer's transfer window. Barca were aware of the drop in the clause and waited to formalise their transfer interest as a result.
And La Liga president Tebas has revealed Atleti have also requested that the organisation block Griezmann from playing for Barca until the issue is resolved.
"Atletico wrote to us asking if we could block Griezmann's license in Barcelona," Tebas told Spanish radio station Onda Cero.
"It is possible to do it. A mechanism has been put in place and the authorities will have to resolve the situation. I have no element of judgment."
Griezmann has headlined a mass exodus from Atleti this close season, with Lucas Hernandez, Rodri, Filipe Luis, Juanfran among the first team regulars to have left.
Joao Felix was drafted in from Benfica as Griezmann's replacement, with Marcos Llorente, Felipe, Hector Herrera, Renan Lodi, Ivan Saponjic and Kieran Tripper also coming in.
Speculation continues to circulate around Atletico's planned move for James Rodriguez, with the Napoli target one of Zinedine Zidane's unwanted men at Real Madrid.
It had been reported this week that the move was close to completion, further underlining the dramatic rebuild Diego Simeone is undertaking in the Spanish capital this year.