President-elect Donald Trump has threatened tariffs of 25% on imports from Canada and Mexico until fentanyl and undocumented migrants stop flowing over US borders. Canada says it has a plan to boost border security — and points to US government data that show most of the problems come from Mexico.

Canadian officials are planning to add patrols, buy new vehicles, and set up emergency reception facilities at the border.

While the announcement is almost certainly bluster to bring attention to illegal immigration and fentanyl smuggling, there are several reasons why it is so risky.

Donald Trump has announced 25% tariffs on Mexico and Canada. Here is how they would work and what such tariffs might mean.