Legal Justice?

Sometime it seems that the justice system we have in our great nation is the "easy way" out for some criminals.. it never really physically hurts them. At the Acme in our neighborhood.. a few guys have been robbing women as they go back to their cars. They will sometime ask if they can walk them to their cars or help with their bags.. then rob them of cash AND groceries.. I mean, yeh, you could call the cops and have them arrested.. but that won't necessarily stop them.. I was talking to a friend about it and we thought it would be cool to bait them.. when we suspect them to be in the lot.. to send a willing girl into the store and on her return.. allow the man to walk to the car and when he attempts to rob her.. we move in.. and beat the piss out of the guy and then.. we call in the police.. I'm sure he would be alot less prone to assume his prior activities after that beating.. cops can't beat a guy and get away with it.. so it needs to be ppl off the street gettin pissed about this guy/guys and doin something about it. And yeh,, its legal.. its called "citizen's arrest" he just happened to resist a little bit.. that's all.