Well... in theory they are limited that way. In practice they can do whatever they want and chock up the discrepancies to "mistakes" in applying the law. Then the loser has to spend thousands on an appeal to get a chance at justice. Also, any investigation into those "mistakes" and any true misconduct are usually so protected that their secrecy outweigh your right to any exculpatory evidence contained in them. Makes you wonder how widespread the mistakes and misconduct are that they want to keep it a secret...