Good for them for exercising their rights for a peaceful protest. I fear that they are misinformed as to what they are protesting though and they may want to do some research before they fly thousands of miles to participate in North Dakota.
There already is a gas pipeline running through that right of way and there has already been two FN approved archaeological studies performed so the burial ground argument is pretty weak. And they are not protesting peacefully in North Dakota. Pipebombs, molotov cocktails, and rocks have been used against peace officers and one protester was charged after she tried to shoot them as well. 
It is funny looking at the signs that these protesters in Anchorage hold. They are anti oil and gas and talk about climate change yet do not hesitate to jump on a plane to fly down. What is their carbon footprint? You cannot say that you dont want oil yet use more than most of us average people.