What’s a ‘Secondary Tariff’ Like the One Trump Imposed on India?

In his second term as US president, Donald Trump has used tariffs as a blanket solution to pursue a wide range of goals: increasing domestic manufacturing and foreign market access, boosting federal revenue, and even punishing the government of Brazil for prosecuting his political ally, former President Jair Bolsonaro. Now he’s deployed a tool he calls a “secondary tariff” in an effort to get countries to distance themselves from US adversaries.

On Aug. 6, Trump announced that such a tariff on imports from India would take effect in 21 days. On top of an existing 25% levy on ...