In order to reduce Heidi Heitcamp’s chances of reelection, North Dakota passed a law requiring proof of address when voting. And the Supreme Court upheld the law (even without Kavanaugh). The problem is that a lot of Native Americans do not receive mail at their homes, and thus do not have what would be considered a regular address.
But there is a way for them to obtain an address:
North Dakota doesn’t have voter registration like other states, so they have until election day to figure this out. Looks like there needs to be an even bigger push for canvasing in North Dakota to get this information out and to get people valid addresses.