A 1930 discrimination statute now taxes Canadian alcohol and dairy at 50% indefinitely

Section 338 duties take effect 30 days after the proclamation date, and July 20 to August 19 is exactly 30 days, so importers got the shortest notice the statute allows ^[3][1][2][1].

The rate is the other boundary. Fifty percent is the maximum the statute permits, and the proclamations set 50% ^[3][1]. For a good that entered duty-free under USMCA in July, the duty went from zero to half of customs value: a shipment appraised at $1 million that cleared free on August 18 owed $500,000 the next day ^[6][3].

Avalara, whose blog post the CPA Practice Advisor article reprints, puts Canadian tariff rates on many U.S. dairy products at 200% to nearly 300%, with only limited volumes entering duty free or at low rates ^[17][14]. A counter-duty cannot reach those levels under this authority, because 50% is the cap ^[4]. Section 338 does hold a blunter instrument: it lets the president exclude articles from importation altogether, and apply duties to a subdivision of a country rather than the whole ^[15].

The statute requires a finding first. The president must find "as a fact" that the other country imposes "any unreasonable charge, exaction, regulation, or limitation which is not equally enforced upon the like articles of every foreign country" ^[9]. The alcohol proclamation said "Canada unreasonably burdens and disadvantages U.S. alcoholic beverages but not alcoholic beverages of other countries", and that starting in March 2025 "all Canadian provinces and territories halted the purchase, distribution, or retailing of U.S. alcoholic beverages" ^[10][11]. Avalara says the provinces did halt sales, and that they acted only after Trump imposed new U.S. duties on many Canadian imports; the proclamation does not say so ^[12].

IEEPA and Section 122 tariffs expire or come up for renewal on a date; Section 338 duties have no such date and can run indefinitely ^[5]. That is what changes a purchasing plan. I would price the 50% as permanent until a proclamation lifts it.

The proclamation power that set the duty can lift it, and because the predicate is a presidential finding, the March 2025 sequence Avalara describes is the fact in dispute if the proclamations are challenged ^[9][12]. The third proclamation has not produced a duty: the White House issued one on motor vehicles, which said "Canada imposed a tariff system on only U.S. motor vehicles", and vehicles were not among the goods that became dutiable on August 19 ^[7][16][8].