The Polish side was kicked out of the competition, despite defeating Celtic 6-1 on aggregate in the qualifying rounds, for fielding an ineligible player.
Celtic have been reinstated into the Champions League and are preparing to face Maribor of Slovenia, but Legia is in the process of appealing against the decision.
The Polish club said in a statement: "Football is our common passion. We are deeply convinced this beautiful game should be based on universal values - shared by everyone who enters the pitch to compete for victory. Those values, widely accepted by the entire European football family, are: football first, fair play and respect.
"Over previous days we have been closely following the decisions of European football authorities. We believe the most crucial element of the game is the result settled in honest and fair competition on the pitch, as highlighted in the UEFA values - 'Football First'!
"We are responsible for the fate of the game and we should all feel obliged to protect the beautiful football heritage based on these superior values for the generations to come.
"We all hope that all decisions made over the next days and forever after will respect the spirit of the game that begins and ends on the pitch. Join us if you support football united around the idea of fair play, respect and sports competition."
UEFA handed Celtic a 3-0 win in the second leg, sending them through on the away goals rule.