I wouldn't have thought that really is the case, and article 21, part 3, I believe gives all the powers that are needed to enable reasonable cooperation with a non-state party. But what's the point of ratifying a convention and then putting so many exemptions in it that you're really destroying the purpose of the convention?
When you're saying that a Canadian officer can direct, or authorize, or request, you're really saying that the Canadian officer can totally destroy the purpose of the convention. Clause 11 goes so far.... I mean, Parliament is not meant to pass contradictory legislation. In this case, on the one hand it's saying yes, we like the convention, it's good, but on the other, we're not quite sure and we're just going to ignore it in a very wide set of circumstances.
I think you're also totally overestimating the likelihood of the United States using cluster munitions. I defy anyone to define “reasonable circumstances” in which there's going to be a reasonable military weapon, in a day and age when the whole thrust of military technology is to achieve more sized weapons, more accurate weapons.