Why does he have to pay if it wasn't illegal yet when he did it? Shouldn't this only matter to future instances of the crime? Kinda like banning guns today and convicting people for the possession of guns tomorrow.
I understand why an exception was made for the nuremberg trials and the "crimes against humanity" which were defined as a crime and applied at that very time, but I don't think simpsons porn (lol@the very idea) is severe enough to play in the same league.
Maybe this is handled differently in Australia. In Germany he would have been judged by the law that was active at the time the crime was committed.
Also, if cartoons are handled like cp now, shouldn't this apply to live-action movies with underage characters (even if the actors portraying them are adults) too? I know a few A titles that would fall into that category then. "American Beauty", "L'amant" (sp?), "The Door in the Floor" with Jeff Bridges and Kim Basinger,... I'm sure there's more, but I can't recall any more off the top of my head.