Using CSS is the easiest, but not the most robust solution.
Admins can and must have ability to do everythings. Moderators are in (almost) same situation with content and users. But both groups are really small and because they must follow rules of a forum then just simple guidance is enough, and staff watches theirs own group. If someone can’t follow such trivial rule could that person follow any other rules either?
So — such option isn’t needed, as I see it.