In the latest twist to an ever more complex and bitter struggle, Sion, who have defied UEFA and FIFA statutes by taking the case to a civil court, accused European football's governing body of "various violations of European Community law".
Sion listed the violations as "unjustified restriction of competition, abuse of a dominant position, violation of the right of access to an independent and impartial judge guaranteed by article 47 of the fundamental charter of rights of the European Union and violation of the right to the free movement of workers... guaranteed by the bilateral agreements between the EU and Switzerland."
Sion President Christian Constantin said: "Two Swiss courts have ruled in our favour but UEFA is not bothered about openly violating these decisions and demands that the Court of Arbitration of Sport (CAS) has the final word."
The case began when Sion signed six new players in the summer despite being subject to a transfer ban imposed by FIFA after the club were ruled to have poached a player from an Egyptian club in 2008.
The Swiss Football League (SFL) initially implemented the FIFA ban but backed down when the players won a civil court ruling in their favour.
Sion fielded some of the players in a Europa League qualifier against Celtic but, after winning the tie, were thrown out of the tournament because UEFA ruled the players were ineligible. The Scottish club took Sion's place.
However, Sion then won an injunction in another Swiss civil court ordering their reinstatement to the Europa League. UEFA has yet to comply with the order.
UEFA has suggested several ways for reinstating Sion but wants the case to be settled at CAS, which has set a hearing for November 24 although Sion have not said whether they will attend.
A further twist came last month when the players were given five-match bans by the Swiss League for breaking its statutes which ban them taking football-related matters to a civil court.
