Specifically "You will need to provide a residence address or specific geographic location information from which your residence address may be determined. The residence address must be in the county in which you are registering."
This clearly allows someone without an "address" to register. In my experience identifying the Post Office on or near the tribe's land is plenty sufficient.
The 'from which your residence address may be determined" reads, to me, like you still need an address. If you don't have a residence address, how can you provide information that determines where it is? It's nonexistent.
https://gis.stackexchange.com/questions/7182/does-an-earthqu...
As far as I know, only homeless people don't have an adress in Denmark.
EDIT: Great, now I'm downvoted as well! Huzzah!