21 U.S.C. § 957: Persons required to register

import into the customs territory of the United States from any place outside thereof (but within the United States), or import into the United States from any place outside thereof, any controlled substance or list I chemical, or export from the United States any controlled substance or list I chemical, An agent or an employee of any importer or exporter registered under section 958 of this title if such agent or employee is acting in the usual course of his business or employment. A common or contract carrier or warehouseman, or an employee thereof, whose possession of any controlled substance or list I chemical is in the usual course of his business or employment. An ultimate user who possesses such substance for a purpose specified in section 802(25) 1 of this title and in conformity with an exemption granted under 1 See References in Text note below. section 956(a) of this title . The Attorney General may, by regulation, waive the requirement for registration of certain importers and exporters if he finds it consistent with the public health and safety; and may authorize any such importer or exporter to possess controlled substances or list I chemicals for purposes of importation and exportation. who is engaged in importing or exporting any controlled substance on the day before the effective date of section 1007 [ May 1, 1971 ], who notifies the Attorney General that he is so engaged, and who is registered on such day under section 510 of the Federal Food, Drug, and Cosmetic Act [ section 360 of this title ] or under section 4722 of the Internal Revenue Code of 1986 [formerly I.R.C. 1954, section 4722 of title 26 ], During the period his provisional registration is in effect under this section, the registration number assigned such person under such section 510 or under such section 4722 (as the case may be) shall be his registration number for purposes of part A of this title [this subchapter]. The provisions of section 304 [ section 824 of this title ], relating to suspension and revocation of registration, shall apply to a provisional registration under this section. the date on which such person has registered with the Attorney General under section 1008 [ section 958 of this title ] or has had his registration denied under such section, or such date as may be prescribed by the Attorney General for registration of importers or exporters, as the case may be,