in canada, the fact is that the british crown bought the land. there are treaties for almost every inch of land outside of bc and quebec, which the british conquered - which is considered lawful under european legal norms stemming from imperial roman law. those ideas don't make sense in the context of indigenous law, but it is the europeans sitting in the castles, applying their laws and they make the rules relative to their culture and norms.

it is also true that the government has repeatedly failed to adhere to the conditions in the treaties, and that in some circumstances it is unclear if the indigenous groups understood what they were signing. the treaties sell or permanently lease the land. that is easy for us to understand, but pre-contact north american indigenous groups had no coherent concept of land ownership. so, how can you sell something if you don't agree you own it?

in traditional indigenous cultures, the land is owned by the gods and humans are only permitted to use it. so, they have concepts of land use but not of land ownership. they also fundamentally share hunting and fishing grounds, which they hold as a commons (an idea that germanic culture had as well, and does continue to tentatively exist in british law).

there are good arguments that the indigenous groups thought they were exchanging the right to use the land in common and not selling it outright, but the courts have not really upheld that and the treaties say what they say. that's where ideas like the honour of the crown come in to enforce some kind of enlightened solution on a shitty situation.

but the lands were not stolen in any coherent legal sense. that's just incorrect.

https://nationalpost.com/news/canada/canadians-reject-that-they-live-on-stolen-indigenous-land-poll