The provisions of this act shall not extend to the territory occupied by the Cherokees, Creeks, Choctaws, Chickasaws, Seminoles, and Osage, Miamies and Peorias, and Sacs and Foxes, in Oklahoma, nor to any of the reservations of the Seneca Nation of New York Indians in the State of New York, nor to that strip of territory in the State of Nebraska adjoining the Sioux Nation on the south added by Executive order.