Here's how Trump's new aggressive tariffs on Mexico will work

The "emergency at the border" has resulted from an influx of migrants traveling through Mexico from Central American countries, many seeking asylum, a form of legal migration, though the president often mischaracterizes it as illegal. The surge of families seeking asylum has strained the system, because the administration treats them like a threat and attempts to detain as many as possible while their claims are adjudicated. Mexican President Andrés Manuel López Obrador has tried to accommodate Trump’s concerns, though he has refused to sign a treaty that would make migrants passing through Mexico to the United States ineligible for American asylum claims. This aggressive step could make him less likely to cooperate with Trump and more likely to retaliate.