The president’s tariffs against China, Mexico and Canada eliminated a trade exemption used by low-cost retailers.

When President Trump pushed ahead with a 10% tariff on all Chinese merchandise, he also closed the century-old de minimis exemption, which allows packages worth under $800 to be shipped into the country duty-free.

Trump revoked a tax loophole that saved companies tens of billions of dollars in fees on imports. Prices on such orders could now go up an average of 30 percent.

The tariffs have also provoked political tension, including retaliation from China, which responded to Trump's move with tariffs on US goods and an anti-monopoly probe of Google, among other measures. The speed with which China filed its complaint with the WTO is an indication of Beijing's readiness for the trade fight.

President Donald Trump has begun his second administration with a series of controversial moves and decisions.