Well Hot Coffee violates the agreement that rockstar signed when they submitted the game for certification. This may even lead to it being pulled in Australia (they have weird ratings). And being reclassified in other countries.
It's the first time anything like this has gotten this sort of media attention and thats thrown up all sorts of questions now on just what sort of mods are being distributed, and how they can hold someone responsible for them. Favourite target right now seems to be whoever made the game.
What no one seems to know is if this was a mod that created or it was simply something to unlock hidden content Rockstar slipped in. Rockstar are denying everything since the whole thing exploded.
<{POST_SNAPBACK}>
Okay, but that is a slightly different legal point. If Rockstar put something in the game and hid it to get around the rating system, then they are rorting the system and need to be punished.
If some modder puts something in their game, not only is the developer/publisher beyond litigation, but (as the modders are just fans doing their own thing) so are the modders. They aren't selling the mods. It's the equivalent to rating private websites for pornography; something that can be done by AOL, but nothing to do with the government.
You'll end up trying to rate mods, and that's more difficult than preventing pr0n on the internet ...