The head coach of the Polish club is furious with the order from European football's governing body that his side must forfeit Wednesday's 2-0 win over Celtic at Murrayfield and see it turned to a 3-0 defeat.
The punishment for fielding suspended defender Bartosz Bereszynski as an 86th-minute substitute puts Legia out of the tournament on away goals.
Legia officials believed Bereszynski had served the three-game ban for being sent off against Apollon Limassol in their final match of the Europa League last season. He missed both ties against Irish side St Patrick's Athletic in the second qualifying round of the Champions League, then sat out the first leg against Celtic, but it transpires he was not registered with Uefa as part of the squad for the meetings with St Pat's.
Celtic are now preparing for a qualifying play-off against NK Maribor, with the first leg in Slovenia on August 20.
Legia, given five days to lodge an appeal with Uefa, are preparing for war, with the Swiss-based Court of Arbitration for Sport already looking a potential port of call.
One-time Rangers defender Berg said: "Uefa are very quick to fly the fair-play flag, but, now they are doing the opposite. It is shocking and contrary to the way European football should be run in terms of fair play and sporting competition."
He added: "For Uefa to make it, with the consequences of it for what has happened, is unbelievable."