Stopping fentanyl from entering the United States presents major challenges, raising the question of what Mexico can actually do to meet President Trump’s demands in order to avoid tariffs.

President Donald Trump has long been touting tariffs as a way to disrupt the flow of fentanyl into the U.S. and this week, he took action with a 10 percent tariff on goods imported from China. But will they really help in the fight to crack down on fentanyl?

The man likely to be named the United States' chief trade negotiator argued Thursday that President Donald Trump's tariff threat against Canada is about fentanyl trafficking.