On July 10, the US and Mexico unveiled new measures to combat the evasion of US tariffs on steel and aluminum, particularly targeting shipments routed through Mexico from countries like China. The new rules stipulate that steel imports from Mexico will face 25% Section 232 tariffs unless proven to have been melted and poured in Mexico, the US, or Canada.

Similarly, aluminum imports from Mexico will be subject to 10% tariffs unless they can certify that primary aluminum wasn't smelted or cast in four specific countries. Importers will now need to furnish a certificate of analysis to US Customs and Border Protection detailing the origin of the metals.