President Donald Trump has justified tariffs on Canadian imports by citing a flood of smuggled fentanyl. But nearly all of the powerful opioid is smuggled from Mexico.

U.S. tariffs on Canada have put experts at odds over how appropriate the action was, particularly given the unaddressed demand side of the fentanyl epidemic.

Canadian and Chinese officials say they were already helping reduce fentanyl smuggling. Prime Minister Justin Trudeau said fentanyl crossing the northern border is "near zero."