18 U.S.C. § 1204 : US Code - Section 1204: International parental kidnapping

      (a) Whoever removes a child from the United States, or attempts
    to do so, or retains a child (who has been in the United States)
    outside the United States with intent to obstruct the lawful
    exercise of parental rights shall be fined under this title or
    imprisoned not more than 3 years, or both.
      (b) As used in this section - 
        (1) the term "child" means a person who has not attained the
      age of 16 years; and
        (2) the term "parental rights", with respect to a child, means
      the right to physical custody of the child - 
          (A) whether joint or sole (and includes visiting rights); and
          (B) whether arising by operation of law, court order, or
        legally binding agreement of the parties.

      (c) It shall be an affirmative defense under this section that - 
        (1) the defendant acted within the provisions of a valid court
      order granting the defendant legal custody or visitation rights
      and that order was obtained pursuant to the Uniform Child Custody
      Jurisdiction Act or the Uniform Child Custody Jurisdiction and
      Enforcement Act and was in effect at the time of the offense;
        (2) the defendant was fleeing an incidence or pattern of
      domestic violence; or
        (3) the defendant had physical custody of the child pursuant to
      a court order granting legal custody or visitation rights and
      failed to return the child as a result of circumstances beyond
      the defendant's control, and the defendant notified or made
      reasonable attempts to notify the other parent or lawful
      custodian of the child of such circumstances within 24 hours
      after the visitation period had expired and returned the child as
      soon as possible.

      (d) This section does not detract from The Hague Convention on
    the Civil Aspects of International Parental Child Abduction, done
    at The Hague on October 25, 1980.