The order throws a wrench in the business models of China-based retailers like Shein and Temu, which were previously exempt from any tariffs and customs inspections thanks to the de minimis loophole.

Boasting an enormous selection of ultra-cheap items at a time when inflation has shrunk household spending power almost everywhere, Shein and Temu have become a global phenomenon.

For now, Temu and Shein’s strategies to go local signal that both companies have been preparing for these regulatory shifts and are taking steps to soften the impact. While critics argue that ...