It doesn't matter if they don't have international standing, what matters is that Canada has recognized them as sovereign entities. You can't be sovereign but then be boxed into the laws of another country
Exactly why they wouldn’t be sovereign nations except by Canada’s niceness. You can only be sovereign by having some form of strong leverage, either resources, power, or international support.
Except for the legal treaties Canada signed with them? This isn't Canada being like gee I guess it'd be woke of us to say you're a separate legal entity. This is based on treaties they've signed and being legally obligated to recognize the rights of a people
Legal treaties, or any kind of contract really, are only worth their paper as long as there is an underlying system with power to enforce them. I believe these nations have no standing in international courts; they have no armies, allies or resources. Upholding these treaties is entirely dependent on goodwill.
If Canada was to ignore them and take over all land, who would stop them? It is, in the end, Canada being nice. Is that such a terrible thing?
Canada is already a federal state with sub national entities that don’t have all the rights of the federal government. Pretty much any state that has a federal system already deals with this.,
