The Cherokee family reservation is sacred land and subject to their own laws. Oklahoma or Federal law is superseded by tribal law....

https://en.wikipedia.org/wiki/Indian_reservation

Because tribes possess tribal sovereignty, even though it is limited, laws on tribal lands vary from the surrounding area. These laws can permit legal casinos on reservations, for example, which attract tourists. The tribal council, not the local or federal government, generally has jurisdiction over reservations. Different reservations have different systems of government, which may or may not replicate the forms of government found outside the reservation. Most Indian reservations were established by the federal government; a limited number, mainly in the East, owe their origin to state recognition.