In a Truth Social post on Saturday, he blasted the Ontario provincial government for not immediately taking down a TV ad that features remarks from former President Ronald Reagan criticizing tariffs.

“Because of their serious misrepresentation of the facts, and hostile act, I am increasing the Tariff on Canada by 10% over and above what they are paying now,” Trump wrote.

He didn’t cite a specific law for the extra levy, and the White House didn’t immediately respond to a request for comment.

But because he is adding it to his existing Canada tariffs, the 10% presumably invokes the International Emergency Economic Powers Act (IEEPA).

Trump also claimed the TV ad was meant to influence the Supreme Court, which will hear arguments on Nov. 5 in a case disputing his ability to invoke IEEPA to justify tariffs.

Peter Harrell, a visiting scholar at Georgetown’s Institute of International Economic Law, pointed out that IEEPA explicitly prohibits its use against information.

“Potential tariffs over a policy TV ad are potentially *even more* illegal than the other tariffs, given that the statute Trump is using, IEEPA, specifically provides that it cannot be used to ‘regulate’ ‘directly or indirectly’ any ‘information or informational materials,'” he posted on X.

The administration has used IEEPA to impose his so-called reciprocal tariffs on countries around the world as well as separate tariffs on Canada, Mexico and China over the fentanyl trade.

Canada currently faces a 35% base tariff rate, but it doesn’t apply to goods that comply with the US-Mexico-Canada Agreement that Trump negotiated in his first term.

Trump’s lack of specifics on his new 10% Canada tariff raised key questions for Erica York, vice president of federal tax policy at the Tax Foundation.

“Is the new 10% tariff on imports from Canada related to the fentanyl emergency or the reciprocal trade emergency or are hurt feelings also now a national emergency?” she asked on X.