President Donald Trump's new tariff orders against Canada, Mexico and China all contain clauses suspending a duty-free exemption for low-value shipments below $800 that is widely seen as a loophole that has allowed shipments of fentanyl and its precursor chemicals into the United States.

Americans consume more illicit drugs per capita than anyone else in the world; about 6% of the U.S. population uses them regularly. One such drug, fentanyl – a synthetic opioid that’s 50 to 100 times more potent than morphine – is the leading reason U.