The authorities of the Spanish capital of Madrid have banned the Estelada, a pro-Catalan independence flag, at Sunday’s national football cup final, angering Barcelona fans and regional authorities, who view the move as an attack on freedom of expression.

The announcement said that no politically charged flags will be allowed at the stadium for the Copa del Rey final on May 22.

Barcelona’s mayor, Ada Colau, and the autonomous region’s president, Carles Puigdemont, said they will be boycotting the match in Madrid in response.

The final will take place at Madrid’s Vicente Calderon Stadium and will see Barcelona face off against Sevilla.

Barcelona’s football club responded by saying, “FC Barcelona expresses, in the most absolute terms, its total and complete disagreement with the announcement,” according to a statement.

“FC Barcelona considers the decision to be an attack on the freedom of expression, the fundamental right of each and every individual to express their ideas and opinions freely and without censorship, a right which is recognized in the Universal Declaration of Human Rights.”

The football club has also called “for the use of common sense” and urged government representatives to create a “good atmosphere at the match.”

This is not the first time the Estelada flag has been banned. Back in 2015, the Catalan club was fined €30,000 ($34,000) by the UEFA after its fans breached article 16 and waved pro-Catalan independence flags during a Champions League final against Juventus in Berlin.

Barcelona’s president reacted by threatening to take the UEFA to the European Court of Human Rights.

Catalonia's parliament backs declaration to split from Spain https://t.co/FyxDYa2rdDpic.twitter.com/oYNXWYscKm — RT (@RT_com) November 9, 2015

Catalonia is one of Spain’s semi-autonomous regions, which has control over its educational and health care systems, as well as police. Catalonia is also Spain’s wealthiest region, producing 20 percent of its national GDP.

Many locals consider the rest of Spain to be an economic burden, and the longstanding independence drive has intensified in recent years due to the economic crisis.

Catalonia’s pro-independence parties, which won a parliamentary majority in a September regional election, have pledged to introduce an 18-month roadmap for independence from Spain by 2017.