Why assume any of the BRAWLERS are the ones breaking the rules? The Brawlers, from what I make up of the text, don't have their own will. Their only input is the way they fight and such. They have no need to be free, for them brawling is all they have, all they can do. They're just trophies, they don't need to eat or sleep, so the only thing they can do is brawl. Perhaps they even enjoy it.
But what if something breaks this lifestyle, something from outside? We all assume the clouded character is something created by breaking the rules, but could it be the other way around? That the clouded character is breaking the rules? Like Sakurai says, in this world, TROPHIES fight. That is the only real rule explained.
Who knows, maybe the clouded character isn't a trophy, but something from "outside", outside this world, outside the rules. Maybe it isn't part of the rule, but it can still break it.
To me, it seems that this is the intro to the first match, where Mario and Kirby encounter this character. Why the Halberd is there, I don't know, maybe it has come to the rescue, and comes after the you have defeated the enemy.