(part 2)  I (personally) also think the tribes are fighting the wrong battle here.  By blocking the pipelines, they are actually putting the environment at MORE risk, not less.  That oil being produced from the Baaken shale will be transported.  The question is how.  Without pipelines, the second safest method is by train, and an even less safe manner is by truck.  Pipelines, by FAR, are the safest means to transport, assuming the systems are built well, with plenty of safety features, and maintained well.  And THAT is a GOOD role for government to play.   

Without that pipeline, the trains and trucks will keep rolling.  And the next time you drive the interstate with your kids in the back seat, take notice of how often you see tanker trucks on the highway, and trains running parallel to your car.  Think about that a bit...