Celtic were knocked out after losing 6-1 on aggregate to Legia in the third qualifying round tie of the competition.
Unregistered defender Bartosz Bereszynski came on as a substitute with three minutes remaining in Legia's 2-0 win in the second leg of the overall 6-1 aggregate triumph.
UEFA investigated the matter and on Friday awarded Celtic the match with a 3-0 victory - making the aggregate score 4-4 and sending the Scottish champions through on the away goals rule after they lost the first leg 4-1.
Celtic will now go into Friday's draw for the final round of qualification matches.