18 U.S.C. § 2252 : US Code - Section 2252: Certain activities relating to material involving the sexual exploitation of minors

      (a) Any person who - 
        (1) knowingly transports or ships using any means or facility
      of interstate or foreign commerce or in or affecting interstate
      or foreign commerce by any means including by computer or mails,
      any visual depiction, if - 
          (A) the producing of such visual depiction involves the use
        of a minor engaging in sexually explicit conduct; and
          (B) such visual depiction is of such conduct;

        (2) knowingly receives, or distributes, any visual depiction
      using any means or facility of interstate or foreign commerce or
      that has been mailed, or has been shipped or transported in or
      affecting interstate or foreign commerce, or which contains
      materials which have been mailed or so shipped or transported, by
      any means including by computer, or knowingly reproduces any
      visual depiction for distribution using any means or facility of
      interstate or foreign commerce or in or affecting interstate or
      foreign commerce or through the mails, if - 
          (A) the producing of such visual depiction involves the use
        of a minor engaging in sexually explicit conduct; and
          (B) such visual depiction is of such conduct;

        (3) either - 
          (A) in the special maritime and territorial jurisdiction of
        the United States, or on any land or building owned by, leased
        to, or otherwise used by or under the control of the Government
        of the United States, or in the Indian country as defined in
        section 1151 of this title, knowingly sells or possesses with
        intent to sell any visual depiction; or
          (B) knowingly sells or possesses with intent to sell any
        visual depiction that has been mailed, shipped, or transported
        using any means or facility of interstate or foreign commerce,
        or has been shipped or transported in or affecting interstate
        or foreign commerce, or which was produced using materials
        which have been mailed or so shipped or transported using any
        means or facility of interstate or foreign commerce, including
        by computer, if - 
            (i) the producing of such visual depiction involves the use
          of a minor engaging in sexually explicit conduct; and
            (ii) such visual depiction is of such conduct; or

        (4) either - 
          (A) in the special maritime and territorial jurisdiction of
        the United States, or on any land or building owned by, leased
        to, or otherwise used by or under the control of the Government
        of the United States, or in the Indian country as defined in
        section 1151 of this title, knowingly possesses, or knowingly
        accesses with intent to view, 1 or more books, magazines,
        periodicals, films, video tapes, or other matter which contain
        any visual depiction; or
          (B) knowingly possesses, or knowingly accesses with intent to
        view, 1 or more books, magazines, periodicals, films, video
        tapes, or other matter which contain any visual depiction that
        has been mailed, or has been shipped or transported using any
        means or facility of interstate or foreign commerce or in or
        affecting interstate or foreign commerce, or which was produced
        using materials which have been mailed or so shipped or
        transported, by any means including by computer, if - 
            (i) the producing of such visual depiction involves the use
          of a minor engaging in sexually explicit conduct; and
            (ii) such visual depiction is of such conduct;

    shall be punished as provided in subsection (b) of this section.
      (b)(1) Whoever violates, or attempts or conspires to violate,
    paragraph (1), (2), or (3) of subsection (a) shall be fined under
    this title and imprisoned not less than 5 years and not more than
    20 years, but if such person has a prior conviction under this
    chapter, section 1591, chapter 71, chapter 109A, or chapter 117, or
    under section 920 of title 10 (article 120 of the Uniform Code of
    Military Justice), or under the laws of any State relating to
    aggravated sexual abuse, sexual abuse, or abusive sexual conduct
    involving a minor or ward, or the production, possession, receipt,
    mailing, sale, distribution, shipment, or transportation of child
    pornography, or sex trafficking of children, such person shall be
    fined under this title and imprisoned for not less than 15 years
    nor more than 40 years.
      (2) Whoever violates, or attempts or conspires to violate,
    paragraph (4) of subsection (a) shall be fined under this title or
    imprisoned not more than 10 years, or both, but if such person has
    a prior conviction under this chapter, chapter 71, chapter 109A, or
    chapter 117, or under section 920 of title 10 (article 120 of the
    Uniform Code of Military Justice), or under the laws of any State
    relating to aggravated sexual abuse, sexual abuse, or abusive
    sexual conduct involving a minor or ward, or the production,
    possession, receipt, mailing, sale, distribution, shipment, or
    transportation of child pornography, such person shall be fined
    under this title and imprisoned for not less than 10 years nor more
    than 20 years.
      (c) Affirmative Defense. - It shall be an affirmative defense to
    a charge of violating paragraph (4) of subsection (a) that the
    defendant - 
        (1) possessed less than three matters containing any visual
      depiction proscribed by that paragraph; and
        (2) promptly and in good faith, and without retaining or
      allowing any person, other than a law enforcement agency, to
      access any visual depiction or copy thereof - 
          (A) took reasonable steps to destroy each such visual
        depiction; or
          (B) reported the matter to a law enforcement agency and
        afforded that agency access to each such visual depiction.