while indigenous law in the states may be a little less developed than it is in canada, the basis of the case appears to be rooted in british imperial law. and, gorsuch' ruling is not all that surprising, when put in context - he's simply asserting the supremacy of congress, as you would expect him to, as a staunch conservative.
but, i can't help but observe that the ruling is essentially rooted in an oversight.
there's an opportunity, here, for america to address what chomsky has called the country's "original sin". yes - maybe, the basis of the ruling is that congress forgot to extinguish the treaty. but, that doesn't mean that congress can't embrace that mistake, and seek to build on it as a new beginning.