American tribes are sometimes called nations within a nation.
Explanation:
Tribes have their own laws and court and they have their own constitution. The Self-Government enables them to be a souvenir and they have been given special status by the US constitution. States don’t intervene much in the tribal Government. But Legislature has the authority to regulate and govern the tribes in US.
The constitution provides special provisions and enjoys jurisdictional powers within their territories. The power to govern the tribes is wholly federal and states cannot interfere in it. Central Government has the complete authority to defend the privileges of the tribe and also constrain any infringements on the tribes.