the ruling is that the indigenous group always owned the land, and europeans just walked in and stole it. an analogy might be helpful.
suppose somebody steals your car, and sells it for a profit. the person that bought the stolen car has somewhat of a problem, in that they purchased stolen goods; they may not have known the goods were stolen, but they are now in unlawful possession of something that was stolen and have to return it if they learn the facts. now, there are two owners of the car - the rightful owner, who had the car stolen, and the person who bought the stolen car. in canadian law, the property must be seized and returned to the rightful owner that had their property stolen and it doesn't matter that you purchased the stolen property, you still have to return it, and can even go to jail if you know the property was stolen and choose to keep it, or evade enforcement around returning it.
i want to reiterate it that: in context, holding to fee simple on stolen property and choosing to evade enforcement is actually a crime that could lead to jail time.
the government never owned the land, so the purchase of it from the crown was invalid. the land was stolen and needs to be returned. the people that purchased the land in fee simple bought land that was stolen, and it's just like buying a stolen car. some maybe didn't know, but most did and, frankly, they ought to be prosecuted for it.
once the property is returned to the party it was stolen from, the question as to compensation for the illegal sale becomes a civil issue, but the buyer really isn't guaranteed to recover those funds. that's what happens when you buy stolen goods from shady sources.