The Swiss club were removed from the competition last Friday after they were adjudged to have fielded ineligible players in the play-off qualifying round against Celtic, a tie they won 3-1 on aggregate.
Sion elected to pursue the matter through the local courts but were rebuffed in their efforts to have the decision overturned.
A statement from the Valais court read: “According to applicable law, the dispute does not have sufficiently close links with the canton of Valais to have a basis of jurisdiction with the local Valais judicial authorities. The measures sought by the applicant were exclusively against UEFA, who have headquarters in Nyon.”
An attempt to bring about a second court case by the ineligible players, who claimed their trade was being restricted by the decision to expel Sion from the competition, is also thought to have been unsuccessful.
But Christian Constantin, the Sion president, has vowed to fight UEFA all the way, even if the Europa League starts without his side next week. “It’s not finished,” he said. “We might not make it to Madrid but perhaps after that the justice system might ask the competition to stop and allow our reintegration. You can start the competition and then a judge might say stop.”
Sion had previously claimed to have also submitted an appeal against their expulsion to UEFA earlier in the week but as Herald Sport went to press last night the governing body had still not received the necessary paperwork ahead of the 11pm deadline.
The Europa League group phase begins on Thursday, with either Celtic or Sion away to Atletico Madrid in the first match. Stade Rennais and Udinese Calcio are the other two teams in Group I.
Sion had been given a transfer embargo for breaching rules over the signing of Essam El-Hadary, the Egyptian goalkeeper, three years ago but the club and FIFA have different interpretations over the length of the ban.
The Swiss Cup winners have already won a civil court ruling over the issue, which prompted their domestic football authorities to allow them to field the affected players and the Swiss club are adamant UEFA also gave them the green light to play them.
Earlier in the week, they released a statement which accused UEFA of trying to take revenge on Constantin, while revealing they had made flight and hotel reservations for Madrid.
It read: “The decision comes from the three UEFA judges who decided to keep Celtic in the competition. For us, it’s a pure revenge against our president. We remind that Celtic received before its home game an official document from the European federation: it mentioned that players were officially eligible. Sion prepares its travel to Madrid.”