The most credible exception to the case for free trade policy is rooted in concerns about national security. If complete freedom of trade jeopardizes our national security, some protectionism arguably is justified because, as even Adam Smith insisted, although free trade is enriching and important, “defence … is of much more importance than opulence.”

As Smith’s statement implies, protectionism pursued for purposes of national defense will reduce the country’s material well-being, but this cost is worth paying if the protectionist measures result in a large enough enhancement of national security. (Caleb Petitt argues, not implausibly, that Smith really didn’t believe that national-security concerns justify a retreat from free trade. But that’s a topic for another time.)

Read the article.