But we adhered to the rules - even checked with UEFA, and they actually assured us that we were abiding by the rules... then UEFA changed the rules.
Let's put it in a simple term, even you might understand...
Say you're on the motorway doing 70mph... quite happy with yourself, because you know the speed limit and you've been checking your speedo, to make sure you haven't exceeded the speed limit...
...then you get pulled over by the police, they give you a fine and 6 points on your licence for speeding – you plead your case because you know you didn't go over 70mph, only for the police to inform you they'd changed the speed limit to 55mph – you'd feel that was unfair I dare say!
Now, apply this to the CAS case... it's the equivalent of the police coming round to your house and trying to fine you again for the offence your paid for years ago.