Granted, the justice system is not flawless.
The problem then is with the law, not the system. Do you want to have an agency that is above the law? Because that is what this argument would seem to imply.
Corruption, such as lobbyists influencing decisions to make certain laws that grant special privleges and such, is harmful to regular people. However, it's not capitalism. Again, the only solution to this is to have someone above the law.
But the problem is minimized, and I don't know of any system that completely eliminates all problems.
I can see why you don't like it. It's not perfect, I can accept that. But what can you do about it? There is no ultimate authority that can catch everything ahead of time, institute justice flawlessly, and all without a great hit to production (well, besides God, or some kind of deity, whatever you believe).
We have never been able to stop corruption in the legislative branch.
We have never been able to stop all fraud with regulation.
Prosecuting fraud itself is a deterrent to fraud. It is the first deterrent. Without it, then there is no deterrent. Regulation goes above and beyond this. It is a further hindrance on production by sacrificing productive capabilities (you need people in order to regulate), and it puts a lot of strain on business to the point that it hurts competition (new firms will find it hard to conform to the laws/regulation).