You're forgetting that Barcelona are a massive money making machine. Would the powers that be risk changing that just because they broke the rules? Not in a month of Sundays.
PTB: "Hey, Barca. You're taking the piss now so you need to be punished. You're getting a signing ban."
Barca: "But that might compromise our ability to keep money pouring into the game."
PTB: "Fair point. Okay then.. appeal the ban, we'll suspend it, you go absolutely mental on the signings and that should sustain you until our meaningless punishment expires."