18 U.S.C. § 373 : US Code - Section 373: Solicitation to commit a crime of violence

      (a) Whoever, with intent that another person engage in conduct
    constituting a felony that has as an element the use, attempted
    use, or threatened use of physical force against property or
    against the person of another in violation of the laws of the
    United States, and under circumstances strongly corroborative of
    that intent, solicits, commands, induces, or otherwise endeavors to
    persuade such other person to engage in such conduct, shall be
    imprisoned not more than one-half the maximum term of imprisonment
    or (notwithstanding section 3571) fined not more than one-half of
    the maximum fine prescribed for the punishment of the crime
    solicited, or both; or if the crime solicited is punishable by life
    imprisonment or death, shall be imprisoned for not more than twenty
    years.
      (b) It is an affirmative defense to a prosecution under this
    section that, under circumstances manifesting a voluntary and
    complete renunciation of his criminal intent, the defendant
    prevented the commission of the crime solicited. A renunciation is
    not "voluntary and complete" if it is motivated in whole or in part
    by a decision to postpone the commission of the crime until another
    time or to substitute another victim or another but similar
    objective. If the defendant raises the affirmative defense at
    trial, the defendant has the burden of proving the defense by a
    preponderance of the evidence.
      (c) It is not a defense to a prosecution under this section that
    the person solicited could not be convicted of the crime because he
    lacked the state of mind required for its commission, because he
    was incompetent or irresponsible, or because he is immune from
    prosecution or is not subject to prosecution.