Spanish outlet Sport 5 reports that there is a legal scenario in which Julián Álvarez could force his exit from Atlético Madrid without the club first receiving his 500 million euro release clause. In that extreme case, the Spanish Football Federation would have to process the transfer, while a Spanish court would later determine how much compensation Atlético is owed.
The report says Mundo Deportivo has already noted that FIFA would not have jurisdiction over a potential dispute between Barcelona and Atlético because it would be an internal matter between two Spanish clubs governed by Spanish law. That means any complaint Atlético might file in Zurich would likely go nowhere, similar to the 2019 Antoine Griezmann case, when FIFA did not intervene and Spain's local federation handled the matter.
Under the relevant royal decree regulating professional athletes in Spain, the release clause is the usual way to end a contract early, and the player is normally responsible for paying it. But Article 16 also allows a player who ends a contract unilaterally, without cause attributable to the club, to trigger compensation for the club instead, with the amount set by labor court if there is no prior agreement. The law says the factors include sporting circumstances, damage to the club, and the reasons for the split.
In the scenario described, Álvarez could terminate his Atlético contract on his own and then sign for Barcelona without any transfer fee being paid upfront. The courts would later set the compensation. The same provision says that if the player signs with another club within a year, that new club is secondarily liable for the financial obligations. The federation would also have to allow the registration process so Álvarez could work while the financial dispute remains unresolved.