I’ve been perusing the U.S. Aluminum Association’s official reaction to U.S. President Donald Trump’s announcement that he intends to impose a 25 per cent tariff on Canadian aluminum. In its way, it’s a small masterpiece of political messaging. The whole idea of a U.S. tariff on Canadian aluminum, which ordinarily makes up 60 per cent of the entire American supply of the metal, flies in the face of a hundred years of industrial development, conscious and explicit partnership between the countries, and all logic. The U.S. defence industry is a particularly heavy user of aluminum, and Canada’s aluminum industry, built with plenty of American capital, is actually defined in U.S. law as being part of the U.S. “industrial base” for national-security purposes.