No one would ever accuse Donald Trump of meticulous adherence to the rules of formal logic. But even the president ought to realize the strongest argument against Trump's tariffs on American imports has been made by Trump himself.

In early May, Trump announced the U.S. was withdrawing from the Iran deal. Among other things, this means the re-imposition of sanctions — the "highest level" of sanctions, as he put it, which he said would be "crippling." Those sanctions include efforts to block Iranian oil sales, limits on Iran's ability to access international banking systems, and measures to prevent Iran from trading with other countries.

That last provision would "have a swift effect on some big companies," Fortune reported. Among them: Boeing and Airbus, which "had been planning to start selling aircraft to the Islamic Republic for the first time." General Electric also will be hit hard: "Not only is it one of the U.S. companies making parts for Airbus, but it has also received big parts orders for oil and gas facilities in Iran." Volkswagen had started selling cars in Iran, and might have to stop. Ditto for the French company that makes Peugeots.

Sanctions such as these will hurt Iran, the administration and others argue, by depriving it not just of oil revenue, but of consumer goods and opportunities for employment.

As one analysis by the Foundation for Defense of Democracies put it in 2014, when the Obama administration was easing sanctions as a carrot to entice Iran to negotiate, the easing of sanctions provided "economic relief. ... The value to the Iranian economy of sanctions relief ... includ[es] employment growth. ... [A] sanction relief provision that allows for the resumption in imports of auto parts ... promotes economic growth since auto parts are used to build cars for domestic consumption. ... [T]he suspension of sector-specific sanctions also provide a boost through facilitating imports into Iran."

Easing import restrictions, the analysis said, made an "equally, if not more important" contribution to economic growth than increased oil sales.

Reimposing sanctions, as Trump wants to do — including sanctions that limit imports — therefore will hurt Iran's economy and put pressure on the company's leaders to change their ways.

But that is the precise opposite of what Trump says about the United States. When it comes to America, the president claims limiting imports will help the country.