Mercury trade is regulated under the Minamata Convention on Mercury, to which the United States is a party. The EPA administers domestic restrictions, and the Mercury Export Ban Act prohibits US export of elemental mercury. Importers of mercury must comply with EPA notification and recordkeeping requirements, and should verify that the source country and intended use are consistent with current treaty obligations and domestic law.

Subheading 280530 covers only the elemental (uncompounded) rare-earth metals, scandium, and yttrium, whether in pure form or as interalloys or mixtures of these metals. Rare-earth oxides, chlorides, carbonates, and other chemical compounds are classified in Chapter 28 under their respective compound headings rather than here. The distinction matters because compound forms are far more commonly traded and may carry different duty rates or trade-remedy exposure.