The way I understand it is, if you've played one game for one team in the CL, you can't play for another CL team if you happen to get transferred during the tournament. Is that correct? What about players who were not on the roster when CL started, are there any restrictions on them?
if you play in a champions league game from the start or are brought on as a sub and move to another club involved in any european competition that season, you are cup tied and cant play, Im actually not sure if its the same for players on the bench that dont get on, I wouldnt think so. Players that arent in the squad arent affected.