U.S. President Donald Trump this week shut a trade loophole that has been used to ship low-value packages duty-free from China, the "de minimis" exemption on import tariffs. Trump's halt to Section 321 de minimis is part of his implementation of an additional 10% tariff on China and 25% tariffs on Canada and Mexico,

Here’s how to understand de minimis and how it turbocharged bargain platforms Shein and Temu.

The trade loophole is meant to ease small-scale sales — but critics say it's been abused and gives Chinese firms an unfair advantage.