Celtic was reinstated in the Europa League on Friday after Swiss side FC Sion was thrown out of the competition for fielding ineligible players.
Sion president Christian Constantin said prior to the verdict that his club would appeal against UEFA's expected decision, prolonging uncertainty before the Europa League group stage kicks off on Sept. 15.
UEFA's disciplinary panel upheld the Glasgow club's protest that Sion selected five players signed in the offseason in last month's two playoff-round matches between the two teams, which was in breach of a FIFA transfer embargo.
Both matches have been awarded as 3-0 wins to Celtic, which played both legs of the playoff under protest.
Sion drew 0-0 in Glasgow before winning the return leg 3-1. Pascal Feindouno, one of Sion's disputed signings, scored twice.
Sion can appeal Friday's ruling to UEFA, then the Court of Arbitration for Sport.
''We are pleased by this decision, the approach which has been taken by UEFA and the fact that UEFA rules and regulations have been upheld,'' Celtic said on its website.
Sion has fought the case since 2009 when FIFA imposed a one-year ban on registering new players.
FIFA ruled that Sion and goalkeeper Essam El-Hadary broke transfer rules when he walked out on Egyptian club Al-Ahly midseason in April 2008 to move to Switzerland.
Sion and El-Hadary challenged FIFA at CAS and Switzerland's supreme court but lost both appeals.
El-Hadary served a four-month ban and was ordered to pay Al-Ahly $796,500 in compensation.
The Swiss Federal Tribunal ruled against Sion in January, when the transfer embargo appeared to finally take effect.
However, Sion now argues that it served the FIFA ban in accumulated time over several transfer periods, and so should have been allowed to register new players in this offseason.
The case was further complicated when Sion's offseason signings won a provisional ruling from a provincial court forcing Swiss football authorities to allow them to play.
Still, FIFA and UEFA insisted that their statutes do not allow civil courts to settle football disputes.
Sion had an asterisk by its name when UEFA conducted the Europa League draw last Friday. It was fourth-seeded in a difficult group with Atletico Madrid, Udinese and Rennes.
Atletico was drawn to host Sion in the first group match on Sept. 15.
