The UN declaration is supported worldwide. We don't have a big dissension anywhere in the whole world on it. If some instrument is supported very strongly by indigenous peoples, and if the world community has also accepted it by reaffirming it 10 times, then that instrument has legitimacy as a human rights instrument.
I think it's very useful to refer to it with the understanding that each different indigenous people will interpret it from their own world view, from their own priorities.