President Trump signed three proclamations Monday targeting different sets of Canadian imports — motor vehicles, alcohol and dairy. The tariffs, which fall under the rarely used Section 338 of the Tariff Act of 1930. …Last week, Trump tore into Canada over the wildfires blazing through northwestern Ontario, which led to major air pollution issues across large areas of the U.S. mainland. …One of the senior officials on Monday specified that the newly announced 50% tariffs on Canadian goods are not related to the wildfires — but added that Trump “has asked for options on that.” Section 338 gives the president the power to impose tariffs on the goods of countries found to be discriminating against the US. The obscure tariff-setting authority has “gone unused for decades,” John Veroneau and Catherine Gibson of law firm Covington and Burling LLP wrote in a 2016 article. They found no public record relating to Section 338 since 1949.

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