18 U.S.C. § 1156

Whoever, except for scientific, sacramental, medicinal or mechanical purposes, possesses intoxicating liquors in the Indian country or where the introduction is prohibited by treaty or an Act of Congress, shall, for the first offense, be fined under this title or imprisoned not more than one year, or both; and, for each subsequent offense, be fined under this title or imprisoned not more than five years, or both. The term “Indian country” as used in this section does not include fee-patented lands in non-Indian communities or rights-of-way through Indian reservations, and this section does not apply to such lands or rights-of-way in the absence of a treaty or statute extending the Indian liquor laws thereto.