18 U.S.C. § 111 : US Code - Section 111: Assaulting, resisting, or impeding certain officers or employees

      (a) In General. - Whoever - 
        (1) forcibly assaults, resists, opposes, impedes, intimidates,
      or interferes with any person designated in section 1114 of this
      title while engaged in or on account of the performance of
      official duties; or
        (2) forcibly assaults or intimidates any person who formerly
      served as a person designated in section 1114 on account of the
      performance of official duties during such person's term of
      service,

    shall, where the acts in violation of this section constitute only
    simple assault, be fined under this title or imprisoned not more
    than one year, or both, and where such acts involve physical
    contact with the victim of that assault or the intent to commit
    another felony, be fined under this title or imprisoned not more
    than 8 years, or both.
      (b) Enhanced Penalty. - Whoever, in the commission of any acts
    described in subsection (a), uses a deadly or dangerous weapon
    (including a weapon intended to cause death or danger but that
    fails to do so by reason of a defective component) or inflicts
    bodily injury, shall be fined under this title or imprisoned not
    more than 20 years, or both.