Why not propose a resolution banning black magic while we're at it? After all, this is just a game!
Doctor Cyclops, more nations overtly engage in black magic than they do in subliminal messaging. Black magic is often times used as a legit weapon of warfare, and in some cases, has replaced technology entirely. Many of these black magicians reside in PT nations who would be incredibly angry if we MT-Muggles attempt to regulate the use of magic. These people would be especially upset if they are part of the WA and also engage in Roleplaying, because they may decide to go into non-compliance, thereby threatening the entire insitution of the General Assembly. If you have seen how the debate over FT space netruality has went, I speculate that such a debate would go in exactly the same method.
A ban on black magic would run into much opposition. It is far better instead to try and regulate something that would have much less supporters, such as subliminal messaging. As of now, we have found no nation here arguing AGAINST the ban on subliminal messaging on the basis of "Subliminal messaging actually helps people out!" I'm having the feeling I should resurrect my old nation, just to provide that debate.