Citing his office’s heavy obligation to keep the homeland secure, members of President Trump’s administration now propose to reduce the flow of foreign-produced automobiles that quietly cross our borders by imposing a 25 percent tariff on each one of them. This presents an interesting question: Where exactly is the line between economic and national security policy?

Even though we produce more than 11 million wheeled vehicles in the United States each year, and even though practically every major foreign auto producer has production taking place on U.S. soil, Secretary of Commerce Wilbur Ross seems to believe they present a national security problem that demands an answer.