Aborigines got Ayer's rock back.  Their motivation was its sacredness (my son is friend to a member of the family that led efforts to reclaim it).  Don't see why the Navajo and their allies can't hang onto their "cathedral" just because it isn't man-made.  Fact that it isn't makes their wishing to keep it even more justifiable, IMHO.  I don't see any Navajo trying to usurp Chicago's Holy Name cathedral.  Perhaps they should.  Fair exchange ain't no robbery.