It is an interesting statement. If you believe in the same classical Hobbesian view of politics that guides the foreign policy of most states he is completely right. As the leviathan he has the ultimate right to do whatever he so pleases, because the monopoly over violence is his alone. So as far as some interpretations of international law are concerned, he was completely justified in his actions and therefore cannot be tried.
Fortunately however he's not being tried by an international court, so he should end up with a punishment as proportionate to his crimes as the undoubtably inventive Iraqis can decide on.