Seems the BATF thinks tribes are under their thumb, but then, that’s no different than how they regard everyone. These aren’t exactly applicable but seem to demonstrate that BATF has no problem enforcing its regs and the federal laws in Indian Country.
“tribal police departments generally do not qualify for the exemption from payment of the transfer tax for NFA firearms, are not eligible to receive firearms interstate, and can not possess a ‘post-1986’ machinegun.”[0]
“federal authorities alleged Ho-Chunk Inc. and its subsidiaries had violated federal tobacco laws by shipping and selling “untaxed, unstamped cigarettes to businesses in Nebraska other states.”[1]
[0] https://www.atf.gov/rules-and-regulations/nfa-transfers-trib...
[1] https://www.indianz.com/News/2019/02/04/winnebago-tribe-stil...