It isn't so much that they're above the law, it's the unwritten code that you don't rat out fellow officers. My father was a cop and he was no angel, and he knew of plenty others who were no angels either. But it's all about the 'brotherhood' and to rat is like the ultimate form of betrayal. Especially if you're just one of those cops that just comes in and does your job the way it should be done...when you rat, the downfall of the department and everything is all on your shoulders.