24 U.S.C. § 154 : US Code - Section 154: Unlawful intrusion, or violation of rules and regulations

      All persons who shall unlawfully intrude upon said reserve, or
    who shall without permission appropriate any object therein or
    commit unauthorized injury or waste in any form whatever upon the
    lands or other public property therein, or who shall violate any of
    the rules and regulations prescribed hereunder, shall, upon
    conviction, be fined in a sum not more than $1,000, or be
    imprisoned for a period not more than twelve months, or shall
    suffer both fine and imprisonment, in the discretion of the court.