Heading 1517 explicitly excludes edible fats and oils from heading 1516. If a blend's primary component is a chemically modified fat (e.g., a fully hydrogenated base), the product may remain in 1516 or shift to 1517 depending on whether the blend constitutes a distinct preparation. The essential-character test under GRI 3 applies, and a binding ruling from CBP is advisable for complex formulations.

Margarine imported for retail sale must comply with FDA's standard of identity for margarine (21 CFR Part 166), which specifies minimum fat content and permitted ingredients. The foreign manufacturer must be registered with FDA under FSMA, and the US importer must have a Foreign Supplier Verification Program in place. Products not meeting the standard of identity cannot be labeled 'margarine' and may require relabeling or refusal of entry.