Customs Bulletin And Decisions, Vol. 53, No. 40, November 6, 2019, contains two items of interest--
In such complex cases CBP often consults the Harmonized Commodity Description and Coding System Explanatory Notes ("ENs") which constitute the "official interpretation of the Harmonized System" at the international level. (See 54 Fed. Reg. 35127, 35128 (Aug. 23, 1989).) While neither legally binding nor dispositive, the ENs "provide a commentary on the scope of each heading" of the HTSUS and are "generally indicative of [the] proper interpretation" of these headings. However, the Harmonized System ("HS") itself, and the U.S. tariff schedule that is based on the HS, the ENs are available only for purchase, and they are quite expensive, 749 Euro. And, as they are periodically updated, that is a recurring cost.