China has thrown a wrench into the global supply chain by slapping new export controls on antimony metals, ores, and oxides, effective September 15. This move could spell trouble for American arms manufacturers who are heavily dependent on this crucial resource. Companies aiming to export these materials will now need to navigate a complex licensing process for dual-use products—a requirement that might not be as benign as it sounds.

The Chinese Commerce Ministry insists that these new r...