18 U.S.C. § 116 : US Code - Section 116: Female genital mutilation

      (a) Except as provided in subsection (b), whoever knowingly
    circumcises, excises, or infibulates the whole or any part of the
    labia majora or labia minora or clitoris of another person who has
    not attained the age of 18 years shall be fined under this title or
    imprisoned not more than 5 years, or both.
      (b) A surgical operation is not a violation of this section if
    the operation is - 
        (1) necessary to the health of the person on whom it is
      performed, and is performed by a person licensed in the place of
      its performance as a medical practitioner; or
        (2) performed on a person in labor or who has just given birth
      and is performed for medical purposes connected with that labor
      or birth by a person licensed in the place it is performed as a
      medical practitioner, midwife, or person in training to become
      such a practitioner or midwife.

      (c) In applying subsection (b)(1), no account shall be taken of
    the effect on the person on whom the operation is to be performed
    of any belief on the part of that person, or any other person, that
    the operation is required as a matter of custom or ritual.