The headline on the Wall Street Journal’s editorial on U.S. President Donald Trump’s 25 per cent tariffs on Canada and Mexico was: The Dumbest Trade War in History.

It points out that Trump’s supposed justification (illegal drugs flowing across the border) for the “economic assault” on Canada and Mexico “makes no sense”; that American industry would be much less competitive without North American trade; that American consumers will suffer; and that countries will be less eager to deal with the United States, given its willingness to ignore its treaty obligations.