The US president has imposed 25% tariffs on Canadian and Mexican imports and threatened to escalate further if the countries retaliated, which they have already done. Is Trump’s move legal? What’s likely to come next?

Trump knows the United States has more leverage over its neighbors than they do over his country. But exploiting that position of strength could cause a historic rupture.

Experts say the 1977 International Emergency Economic Powers Act is untested for imposing import tariffs and Trump's action will likely face swift court challenges that could set important precedents.