How to legally challenge Trump’s Canada and Mexico tariffs 

President Trump’s tariffs on Canada and Mexico, imposed because of fentanyl and illegal immigration, should be legally challenged. Observers worry, however, that courts will be deferential to the sweeping powers granted to the executive under the International Emergency Economic Powers Act. 

This concern overlooks the fact that Trump’s executive order includes an escalation mechanism for Canada and Mexico. It allows Trump to increase his tariffs if Canada or Mexico retaliates. 

This tit-for-tat is about waging a trade war, not solving a national emergency. And there’s no way to square it with the letter or spirit of the International Emergency Economic Powers Act. 

Crafting a narrower argument about the escalation mechanism, rather than about whether the act allows for tariffs, would be easier, largely yield the same result and raise broader questions about the legislation. 

Calls to challenge Trump’s tariffs based on the act are growing by the day. A recent Wall Street Journal editorial tapped widespread sentiment in pitching a case. 

But the hesitancy on the part of would-be plaintiffs is obvious. While Trump’s tariffs are unprecedented, and might even be illegal, the legislation is vague, and no court has ruled against a president’s declaration of a national emergency under the International Emergency Economic Powers Act. 

Focusing on the escalation mechanism largely sides-steps these pitfalls. Rather than raising questions about the act writ large, the argument would be that one-upping Canada’s and Mexico’s tariff reprisals has nothing to do with fentanyl or illegal immigration. It’s about waging a trade war. 

This same logic is currently being argued before the U.S. Court of Appeals for the Federal Circuit in a case that may go to the Supreme Court. The irony is that this case is about two of four rounds of Section 301 tariffs that Trump slapped on China in his first term. 

Back in 2020, U.S. vinyl tile manufacturer HTMX went to the U.S. Court of International Trade to get a tariff refund for most Section 301 tariffs. 

It argued that the third and fourth rounds were used to clean up the mess caused by the first and second rounds, which led China to retaliate. Specifically, HTMX explained that the third and fourth rounds gave rise to “an unprecedented, unbounded and unlimited trade war.” 

The court didn’t disagree, but said it would “not try to unscramble this egg.” Instead, it asked the United States Trade Representative to do a better job connecting more dots. It said China’s retaliation was “inextricably” linked to the actions that had originally given rise to the Section 301 tariffs and were thus legal. But this was a stretch, hence the appeal. 

It’s true that Section 301 tariffs can be modified, including when the policies and practices “that are the subject of such action has increased or decreased.” But fine-tuning these tariffs to deal with changing circumstances is not what happened with China.

The third and fourth rounds of tariffs were about China’s retaliation, not Beijing’s failure to comply with the first rounds. As the Court of International Trade said, “China directly connected its retaliation to the U.S. action and to its own acts, policies, and practices that the U.S. action was designed to eliminate.”

The escalation mechanism in Trump’s executive order is even more untethered to compliance than the latter rounds of the Section 301 tariffs on China. It’s the Achilles heel of these International Emergency Economic Powers Act tariffs. Courts can condemn them without having to conclude that tariffs can’t ever be used under the act. 

Litigation is no substitute for legislation. Congress must do its job to rein in abuses of the International Emergency Economic Powers Act. The Protecting Americans from Tax Hikes on Imported Goods Act of 2025 is a useful start.

Yet, until Congress acts to claw back its tariff authority, it will fall on the courts to deny the executive a free hand to wage an all-out trade war.

Marc L. Busch is the Karl F. Landegger Professor of International Business Diplomacy at the Walsh School of Foreign Service, Georgetown University.