Right. Well, “notwithstanding” can mean various things under labour laws, constitutional law, international law.
This treaty came through a series of negotiations with amendments and compromises. The Canadian negotiator definitely did not want article 21 to become a loophole. He defended it against civil society groups, who said to watch about the danger here. He said, “No, this is not the Canadian intention.” He gave all the speeches on behalf of Canada during the Oslo negotiations and the other negotiations, and he sees that this is not an exception. Notwithstanding doesn't mean exception; it just means that article 21 allows you to participate in multinational coalitions that otherwise some countries might have been hesitant about, because if the Americans are going to use cluster munitions over there, maybe we can't participate.
This says that you can still participate in a multinational coalition, but it doesn't say that you can all of a sudden violate the basic provision of the convention, which is to not, under any circumstance, use cluster munitions.