IMHO a good idea to ban them but not for the reason you state. Strictly for Health Safety reasons. There's no way some ice in a small cooler can safely cool the meat added within the 2 and 4 hour windows.
This was discussed a couple of years ago by the BOD. They felt it was up to each organizer to make a ruling as they are the ones who would get sued if a judge gets sick.
If you were paying attention this year you saw the SAMS contests did ban coolers and health safety was the reason (or should I say their worry about liability if a judge got sick).
Retired competition cook. BBQ mentor.