Spanish football federation announced that there will not be restrictions on the number of non-EU players as it classed the game as "not professional".
It remains to be seen what's their final squad for the game.
A Sevilla club statement read: "Sevilla FC is surprised by the RFEF's statement 24 hours before the Super Cup".
Sevilla qualified for the Supercopa as runners-up of the Copa del Rey following Barcelona's domestic double.
But Barcelona are keen to avoid any clashes with Sevilla and have erred on the side of caution by leaving Malcom out of the squad and have chose to start Arthur, while Coutinho and Vidal have been named as substitutes.
"The club's legal department is studying the matter and should FC Barcelona submit a team with more than three non-EU players, it would present possible ground for the filing of a complaint on account of an improper line up".
Forwards Lionel Messi and Luis Suarez have already acquired European Union citizenship while Brazilian Phlippe Coutinho has received a Portuguese citizenship through his wife.
Despite the adjustment potentially giving his side an edge, Barca boss Valverde is also far from content.
The Argentina worldwide takes over from Iniesta following his move to Vissel Kobe in the J League at the end of the 2017-18 campaign.