Donald Trump’s tariffs are a headache for all his trade partners. But the U.S. president’s plan to impose ad hoc “reciprocal” levies on imports are a particular problem for the European Union. By enabling him to target whichever countries in the bloc he pleases,

President Donald Trump’s shift in policy to reciprocal tariffs is a relief to markets, U.S. consumers and most trading partners.

Here’s what you need to know about reciprocal tariffs and who might be impacted by Trump’s plan. Reciprocal tariffs refer to tariffs—the taxes charged on imported goods—the U.S. government plans to levy against global trading partners that are equal to the existing tariffs foreign countries have set against American goods.