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.

Days before tariffs that have the potential to cripple Canada's economy are expected to come into effect, Canadian politicians are pushing the message that the country is cracking down on one of U.S.