19 U.S.C. § 81c

(a) Handling of merchandise in zone; shipment of foreign merchandise into customs territory; appraisal; reshipment to zone Foreign and domestic merchandise of every description, except such as is prohibited by law, may, without being subject to the customs laws of the United States, except as otherwise provided in this chapter, be brought into a zone and may be stored, sold, exhibited, broken up, repacked, assembled, distributed, sorted, graded, cleaned, mixed with foreign or domestic merchandise, or otherwise manipulated, or be manufactured except as otherwise provided in this chapter, and be exported, destroyed, or sent into customs territory of the United States therefrom, in the original package or otherwise; but when foreign merchandise is so sent from a zone into customs territory of the United States it shall be subject to the laws and regulations of the United States affecting imported merchandise: Provided , That whenever the privilege shall be requested and there has been no manipulation or manufacture effecting a change in tariff classification, the appropriate customs officer shall take under supervision any lot or part of a lot of foreign merchandise in a zone, cause it to be appraised and taxes determined and duties liquidated thereon. Merchandise so taken under supervision may be stored, manipulated, or manufactured under the supervision and regulations prescribed by the Secretary of the Treasury, and whether mixed or manufactured with domestic merchandise or not may, under regulations prescribed by the Secretary of the Treasury, be exported or destroyed, or may be sent into customs territory upon the payment of such liquidated duties and determined taxes thereon. If merchandise so taken under supervision has been manipulated or manufactured, such duties and taxes shall be payable on the quantity of such foreign merchandise used in the manipulation or manufacture of the entered article. Allowance shall be made for recoverable and irrecoverable waste; and if recoverable waste is sent into customs territory, it shall be dutiable and taxable in its condition and quantity and at its weight at the time of entry. Where two or more products result from the manipulation or manufacture of merchandise in a zone the liquidated duties and determined taxes shall be distributed to the several products in accordance with their relative value at the time of separation with due allowance for waste as provided for above: Provided further , That subject to such regulations respecting identity and the safeguarding of the revenue as the Secretary of the Treasury may deem necessary, articles, the growth, product, or manufacture of the United States, on which all internal-revenue taxes have been paid, if subject thereto, and articles previously imported on which duty and/or tax has been paid, or which have been admitted free of duty and tax, may be taken into a zone from the customs territory of the United States, placed under the supervision of the appropriate customs officer, and whether or not they have been combined with or made part, while in such zone, of other articles, may be brought back thereto free of quotas, duty, or tax: Provided further , That if in the opinion of the Secretary of the Treasury their identity has been lost, such articles not entitled to free entry by reason of noncompliance with the requirements made hereunder by the Secretary of the Treasury shall be treated when they reenter customs territory of the United States as foreign merchandise under the provisions of the tariff and internal-revenue laws in force at that time: Provided further , That under the rules and regulations of the controlling Federal agencies, articles which have been taken into a zone from customs territory for the sole purpose of exportation, destruction (except destruction of distilled spirits, wines, and fermented malt liquors), or storage shall be considered to be exported for the purpose of— (1) the draw-back, warehousing, and bonding, or any other provisions of the Tariff Act of 1930, as amended, and the regulations thereunder; and (2) the statutes and bonds exacted for the payment of draw-back, refund, or exemption from liability for internal-revenue taxes and for the purposes of the internal-revenue laws generally and the regulations thereunder. Such a transfer may also be considered an exportation for the purposes of other Federal laws insofar as Federal agencies charged with the enforcement of those laws deem it advisable. Such articles may not be returned to customs territory for domestic consumption except where the Foreign-Trade Zones Board deems such return to be in the public interest, in which event the articles shall be subject to the provisions of paragraph 1615(f) of section 1201 of this title : Provided further , That no operation involving any foreign or domestic merchandise brought into a zone which operation would be subject to any provision or provisions of section 1807, chapter 15, chapter 16, chapter 17, chapter 21, chapter 23, chapter 24, chapter 25, chapter 26, or chapter 32 of the Internal Revenue Code if performed in customs territory, or involving the manufacture of any article provided for in paragraphs 367 or 368 of section 1001 of this title , shall be permitted in a zone except those operations (other than rectification of distilled spirits and wines, or the manufacture or production of alcoholic products unfit for beverage purposes) which were permissible under this chapter prior to July 1, 1949 : Provided further , That articles produced or manufactured in a zone and exported therefrom shall on subsequent importation into the customs territory of the United States be subject to the import laws applicable to like articles manufactured in a foreign country, except that articles produced or manufactured in a zone exclusively with the use of domestic merchandise, the identity of which has been maintained in accordance with the second proviso of this section may, on such importation, be entered as American goods returned: Provided, further , That no merchandise that consists of goods subject to USMCA drawback, as defined in section 4534(a) of this title , that is manufactured or otherwise changed in condition shall be exported to a USMCA country, as defined in section 4502 of this title , without an assessment of a duty on the merchandise in its condition and quantity, and at its weight, at the time of its exportation (or if the privilege in the first proviso to this subsection was requested, an assessment of a duty on the merchandise in its condition and quantity, and at its weight, at the time of its admission into the zone) and the payment of the assessed duty before the 61st day after the date of exportation of the article, except that upon the presentation, before such 61st day, of satisfactory evidence of the amount of any customs duties paid or owed to the USMCA country on the article, the customs duty may be waived or reduced (subject to section 4534(e) of this title ) in an amount that does not exceed the lesser of (1) the total amount of customs duties paid or owed on the merchandise on importation into the United States, or (2) the total amount of customs duties paid on the article to the USMCA country: Provided, further , That, if Canada ceases to be a USMCA country and the suspension of the operation of the United States-Canada Free-Trade Agreement thereafter terminates, with the exception of drawback eligible goods under section 204(a) of the United States-Canada Free-Trade Agreement Implementation Act of 1988, no article manufactured or otherwise changed in condition (except a change by cleaning, testing or repacking) shall be exported to Canada during the period such Agreement is in operation without the payment of a duty that shall be payable on the article in its condition and quantity, and at its weight, at the time of its exportation to Canada unless the privilege in the first proviso to this subsection was requested: Provided further , That no merchandise that consists of goods subject to Chile FTA drawback, as defined in section 203(a) of the United States-Chile Free Trade Agreement Implementation Act, that is manufactured or otherwise changed in condition shall be exported to Chile without an assessment of a duty on the merchandise in its condition and quantity, and at its weight, at the time of its exportation (or if the privilege in the first proviso to this subsection was requested, an assessment of a duty on the merchandise in its condition and quantity, and at its weight, at the time of its admission into the zone) and the payment of the assessed duty before the 61st day after the date of exportation of the article, except that the customs duty may be waived or reduced by (1) 100 percent during the 8-year period beginning on January 1, 2004 ; (2) 75 percent during the 1-year period beginning on January 1, 2012 ; (3) 50 percent during the 1-year period beginning on January 1, 2013 ; and (4) 25 percent during the 1-year period beginning on January 1, 2014 . (b) Applicability to bicycle component parts The exemption from the customs laws of the United States provided under subsection (a) shall not be available on or before December 31, 1992 , to bicycle component parts unless such parts are reexported from the United States, whether in the original package, as components of a completely assembled bi­cycle, or otherwise. (c) Articles manufactured or produced from de­natured distilled spirits withdrawn free of tax from distilled spirits plant; products unfit for beverage purposes (1) Notwithstanding the provisions of the fifth proviso of subsection (a), any article (within the meaning of section 5002(a)(14) of title 26 ) may be manufactured or produced from denatured distilled spirits which have been withdrawn free of tax from a distilled spirits plant (within the meaning of section 5002(a)(1) of title 26 ), and articles thereof, in a zone. (2) Notwithstanding the provisions of the fifth proviso of subsection (a), distilled spirits which have been removed from a distilled spirits plant (as defined in section 5002(a)(1) of title 26 ) upon payment or determination of tax may be used in the manufacture or production of medicines, medicinal preparation, food products, flavors, or flavoring extracts, which are unfit for beverage purposes, in a zone. Such products will be eligible for drawback under the internal revenue laws under the same conditions applicable to similar manufacturing or production operations occurring in customs territory. (d) Foreign trade zones In regard to the calculation of relative values in the operations of petroleum refineries in a foreign trade zone, the time of separation is defined as the entire manufacturing period. The price of products required for computing relative values shall be the average per unit value of each product for the manufacturing period. Definition and attribution of products to feedstocks for petroleum manufacturing may be either in accordance with Industry Standards of Potential Production on a Practical Operating Basis as verified and adopted by the Secretary of the Treasury (known as producibility) or such other inventory control method as approved by the Secretary of the Treasury that protects the revenue. (e) Production equipment (1) In general Notwithstanding any other provision of law, if all applicable customs laws are complied with (except as otherwise provided in this subsection), merchandise which is admitted into a foreign trade zone for use within such zone as production equipment or as parts for such equipment, shall not be subject to duty until such merchandise is completely assembled, installed, tested, and used in the production for which it was admitted. (2) Admission procedures The person who admits the merchandise described in paragraph (1) into the zone shall, at the time of such admission, certify to the Customs Service that the merchandise is admitted into the zone pursuant to this subsection for use within the zone as production equipment or as parts for such equipment and that the merchandise will be entered and estimated duties deposited when use of the merchandise in production begins. (3) Entry procedures At the time use of the merchandise in production begins, the merchandise shall be entered, as provided for in section 484 of the Tariff Act of 1930 [ 19 U.S.C. 1484 ], and estimated duties shall be deposited with the Customs Service. The merchandise shall be subject to tariff classification according to its character, condition, and quantity, and at the rate of duty applicable, at the time use of the merchandise in production begins. (4) Foreign trade zone For purposes of this subsection, the term “foreign trade zone” includes a subzone.