Sion were excluded from the tournament on September 2nd for fielding ineligible players, with Scottish side Celtic promoted to the competition in their place.
"The civil court has this morning ordered UEFA to admit FC Sion as a participant of the UEFA Europa League 2011-2012 and to take all necessary measures to integrate it in the UEFA Europa League group in which FC Sion has qualified," the club said.
"The Canton de Vaud Tribune also orders UEFA to consider the players Stefan Glarner, Billy Ketkeophomphone, Mario Mutsch, Pascal Feindouno, Jose Goncalves and Gabri as eligible as FC Sion players and to admit them in the 2011-12 UEFA Europa League.
"The order has been declared immediately binding."
Sion beat Celtic 3-1 on aggregate in the play-offs but were expelled for fielding ineligible players after signing six players when FIFA stated they were in the midst of a transfer embargo.
UEFA's appeals body are currently hearing the Swiss club's appeal against their expulsion ahead of Thursday's opening group game against Atletico Madrid.
Celtic are currently preparing for the game in Spain but Sion president Christian Constantin has said his side also intend to travel to the Spanish capital.
If their current appeal fails, Sion are able to take the case to the Court of Arbitration for Sport (CAS) in Lausanne.