The Department of Justice now allow American Indian tribes to grow and sell marijuana on reservation land. The new policy will allow the tribes to grow and sell cannabis in they can effectively regulate and maintain the system and follow eight "NO" that currently apply to those states, where cannabis is legal. That include sale to people in states where cannabis is still illegal and sale to minors.
There are 326 recognized tribes in the United States, but it remains unknown how many of them will take an advantage of an opportunity. Maybe soon you will see Indian marijuana dispensary next to tax-free cigarettes and casinos.