No, I can't think of any country offhand that has actually said it would not allow Ahmadinejad to visit. I do know that with the President of Sudan there is this international arrest warrant, which means that states party to this agreement would have to cooperate. If al-Bashir were to show up in Canada, we, in order to comply with that treaty, would have to hand him over to the court. So I assume he wouldn't want to come here, and the issue of banning him wouldn't necessarily arise.
Of course, there was the case of Pinochet, a former president of Chile who was prosecuted. There was an extradition request to Spain that was taken quite seriously.
It's not just that I don't know. Typically, watch lists are not made public. I couldn't tell you, and I suspect you couldn't tell me, who is banned from Canada. Occasionally, a case flares up because somebody tries to get here, like Mr. Galloway, and then is turned away. The list is not normally made public.
I'm not just suggesting that he be put on the list. I'm suggesting that there be some sort of public statement that he's on the list so that the world will know. For all I know, because the list is not public, he may already be on the Canada list. If he is, though, it should be made public.