19 CFR § 10.425 - Transit and transshipment of non-originating cotton or man-made fiber fabric or apparel goods.
(a) General. A good will not be considered eligible for preferential tariff treatment under an applicable TPL by reason of having undergone production that occurs entirely in the territory of Chile, the United States, or both, that would enable the good to qualify for preferential tariff treatment if subsequent to that production the good undergoes further production or any other operation outside the territories of Chile and the United States, other than unloading, reloading, or any other process necessary to preserve the good in good condition or to transport the good to the territory of Chile or the United States.
(b) Documentary evidence. An importer making a claim for preferential tariff treatment may be required to demonstrate, to CBP's satisfaction, that no further production or subsequent operation, other than permitted under paragraph (a) of this section, occurred outside the territories of Chile or the United States. An importer may demonstrate compliance with this section by submitting documentary evidence. Such evidence may include, but is not limited to, bills of lading, packing lists, commercial invoices, and customs entry and exit documents.