True, but for some reason the officers are to dam dumb to enforce it. Look at the pictures taken in the prison. If I was the company command they would understand quickly how it felt to hide something that was not part of your uniform and equipment. Setting on a camera all day would do wonders.
The problem with the computer picture was that it was already taken, thus he was ordering evidence destroyed. Stopping the picture taking on duty is not destroying evidence.
No, regulations state that troops may not store photographs of dead Iraqis. Regulations do not just cover taking pictures. Saying that Lt Grayson destroyed evidence is hindsight and I believe that's what his court martial will establish.