8 U.S.C. § 1557

For the purpose of regulating and preventing the transportation in foreign commerce of alien women and girls for purposes of prostitution and debauchery, and in pursuance of and for the purpose of carrying out the terms of the agreement or project of arrangement for the suppression of the white-slave traffic, adopted July 25, 1902 , for submission to their respective governments by the delegates of various powers represented at the Paris Conference and confirmed by a formal agreement signed at Paris on May 18, 1904 , and adhered to by the United States on June 6, 1908 , as shown by the proclamation of the President of the United States dated June 15, 1908 , the Commissioner of Immigration and Naturalization is designated as the authority of the United States to receive and centralize information concerning the procuration of alien women and girls with a view to their debauchery, and to exercise supervision over such alien women and girls, receive their declarations, establish their identity, and ascertain from them who induced them to leave their native countries, respectively; and it shall be the duty of said Commissioner of Immigration and Naturalization to receive and keep on file in his office the statements and declarations which may be made by such alien women and girls, and those which are hereinafter required pertaining to such alien women and girls engaged in prostitution or debauchery in this country, and to furnish receipts for such statements and declarations provided for in this Act to the persons, respectively, making and filing them.