Crystal Palace chairman Steve Parish has described the decision to exclude the club from next season's Europa League as "the biggest injustice in the history of football."
The Eagles were relegated to the Conference League by UEFA on Friday for violating multi-club ownership regulations.
American businessman John Textor holds a stake in both Crystal Palace and French club Lyon, which also qualified for the Europa League.
"We're devastated," Parish told Sky Sports. "It's a bad day for football. It's a terrible injustice. I believe nobody wants to see this. I don't think UEFA wants this. We've been excluded from a European competition on a ridiculous technicality. Supporters of all clubs should be devastated for us."
Nottingham Forest, who finished seventh in the Premier League last season, may replace FA Cup winners Palace in the Europa League.
UEFA stated that the Eagles could appeal the decision through the Court of Arbitration for Sport, and Parish confirmed their intent to do so.
The rules of European football's governing body stipulate that clubs owned or significantly influenced by the same entity cannot compete in the same European competition.
UEFA set a deadline of March 1, 2025, for clubs to demonstrate restructuring of multi-club ownership, which Palace failed to meet.
Palace argued that Textor does not exert decisive influence over the club, but this defense was not accepted.
"Everyone knows we're not part of a multi-club setup," Parish added. "We don't share any staff. We're caught up in a rule that wasn't intended for us. I don't understand why the panel reached this conclusion. I believe we've shown John had no influence over our club."
"This decision is ludicrous. We will request the appeal court to hear our argument."
Lyon, who also qualified for the Europa League, take precedence over Palace due to their higher league finish in the previous season.
The seven-time French champions finished sixth in Ligue 1, while Palace finished 12th in the Premier League but qualified for European competition by winning the FA Cup.
Earlier this week, Lyon won their appeal against relegation from Ligue 1 after being demoted due to financial issues.
Had their relegation been upheld, they had agreed with UEFA to be excluded from the Europa League, which would have allowed Palace to participate.
English football has two allocated Europa League spots, with Aston Villa securing the other after finishing sixth in the table, one point ahead of Forest.
How did we get here?
Palace were considered underdogs in the FA Cup, defeating Manchester City 1-0. However, their joy at qualifying for Europe for the first time quickly turned to concern when the club realized their spot might be in jeopardy.
UEFA's regulations on multi-club ownership and European competitions are intended to prevent collusion.
According to the governing body's rulebook, a club must prove they are not "simultaneously involved in any capacity whatsoever in the management, administration, and/or sporting performance of more than one club participating in a UEFA club competition."
Textor's Eagle Football owns a 43% stake in Palace and a 77% stake in Lyon, but the Premier League side argued they operate entirely independently.
Forest sought clarity from UEFA in June regarding Palace's European position. Their owner, Evangelos Marinakis, who controls the Greek side Olympiakos, avoided multi-club ownership regulations by diluting his control of the Premier League side.
Textor took similar steps to aid Palace's prospects by agreeing to sell his 43% stake to New York Jets owner Woody Johnson in June, though the deal has not yet been finalized.
Textor later resigned from his leadership role at Lyon.
UEFA postponed its decision on Palace's status until the outcome of Lyon's domestic case, while Parish's side indicated they would likely pursue legal action if their Europa League place was revoked.
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