So what you're saying is that the original Canadian government should have slaughtered the Indians, like they did down south in the US. Then there would be no question of ownership. Because, they were not "defeated" is not relevant (and the natives generally were not at war with the British, so who was there to defeat?). 

The constitution is legally relevant - and native people don't own the land, especially where Title has not been proven in Court, like in this case (and Canada still has rights to proceed with projects even on titled land). It is possible that another first nation other than the Gixtan could gain title in this area (since there are overlapping "claims" everywhere in BC). These two supposed chiefs would then have no say in the matter of the LNG terminal. Even though indigenous people have not always been treated fairly in the past does not put them above the rules of the present.