According to UEFA regulations, an individual or organization is not allowed to control two clubs participating in a continental tournament, to ensure fairness and avoid conflicts of interest.
In this case, American businessman John Textor was identified as affecting both Olympique Lyon and Crystal Palace. Lyon qualified for the Europa League in 6th place in Ligue 1, while Crystal Palace qualified for the FA Cup.
Although Textor sold most of his stake in Crystal Palace to billionaire Woody Johnson for 260 million USD, he still holds a 25% stake and is assessed by UEFA to have a significant impact on the team's operations. This violated cross-ownership regulations and caused Palace to be eliminated from the tournament.
Previously, there was a possibility that Lyon would not be eligible to participate when being proposed for relegation for violating financial rules in France. However, after being allowed to stay in Ligue 1, Lyon are still eligible to play in the Europa League. Therefore, Crystal Palace became the team eliminated according to the general owner's rule.
Nottingham Forest are likely to be promoted to the Europa League to replace Crystal Palace.
UEFA confirmed Palace have the right to appeal to the Court of Arbitration for Sport (CAS). However, considering the recent precedent, in which CAS kept the same sentence for Drogheda United (Ireland) for the same reason, the possibility of overturning the decision is not high.
Losing a Europa League spot is a significant blow for Crystal Palace, especially as the team has just had a successful season under coach Oliver Glasner.