19 CFR § 123.12 - Entry of foreign locomotives and equipment in international traffic.
(a) Use on a continuous route. Foreign locomotives or other foreign railroad equipment in use on a continuous route crossing the boundary into the United States shall be admitted without formal entry or the payment of duty to proceed to the end of the run and depart for a foreign country, in accordance with the following:
(1) On inward trip. Unless formally entered and cleared through Customs into the United States, or unless exempt from entry as provided in § 141.4(b)(4) of this chapter, a foreign locomotive shall be used on the inward trip only in connection with taking the inbound train to the last place in a continuous haul, including the switching of cars which it has hauled into the United States. Other foreign railroad equipment may proceed to the place of complete unloading for any merchandise imported therein.
(2) On outward trip. Unless formally entered and cleared through Customs into the United States, or unless exempt from entry as provided in § 141.4(b)(4) of this chapter, foreign locomotives may be used on the outward trip only in connection with through trains crossing the boundary, including switching to make up such trains. Other foreign railroad equipment may be used in such trains or for such local traffic as is reasonably incidental to its economical and prompt departure for a foreign country.
(b) Admission of empty equipment. Empty foreign railroad equipment shall be admitted to the United States without formal entry and payment of duty only if:
(1) The passengers or goods to be loaded are to be transported directly to or through a foreign country; or
(2) The equipment is exempt from entry as provided in § 141.4(b)(4) of this chapter.
(c) Penalty for improper use. The use of any foreign locomotive and other foreign railroad equipment in violation of this section may result in liabilities being incurred under section 592, Tariff Act of 1930, as amended (19 U.S.C. 1592).
(d) Domestic and foreign locomotives and other railroad equipment defined. For the purpose of this section and § 123.13, locomotives or other railroad equipment manufactured in, or regularly imported into, the United States, shall be considered “domestic” if not subsequently formally entered and cleared through foreign customs into another country, nor used in foreign local traffic otherwise than as an incident of the return of the equipment to the United States. Other locomotives and railroad equipment shall be considered “foreign”.