Depredation Emergency Rule?

Some buddies of mine just got done hunting does on depredation tags up here. They used high powered rifles. I explained to them that I had read that there was an emergency rule that banned the use of high powered rifles on these hunts. I had read that on this forum on another ask the C.O. question.

Could one of you C.O.s point me to the emergency rule? I'd like to show it to them, not to get them in trouble, but to inform them so that next time they use the right weapons.

Thanks!