Trump Threatens 50% Tariffs on Iran Arms Suppliers—But Has No Legal Authority to Do It

Donald Trump announced Wednesday he would slap 50% tariffs on imports from countries supplying Iran with military weapons—a threat that legal experts say he has no authority to carry out.

The declaration came just hours after Trump agreed to a two-week ceasefire with Tehran, posted to Truth Social with his characteristic bluster: "A Country supplying Military Weapons to Iran will be immediately tariffed, on any and all goods sold to the United States of America, 50%, effective immediately. There will be no exclusions or exemptions!"

There's one problem: the Supreme Court already shut down Trump's ability to do this.

No Legal Authority After Supreme Court Ruling

In February, the Supreme Court struck down Trump's use of the International Emergency Economic Powers Act (IEEPA) to impose broad global tariffs, ordering refunds of some $166 billion collected over a year. The 1977 law has been used for decades to back financial sanctions against Iran, Russia, and North Korea—but the court ruled Trump overstepped his authority by weaponizing it for trade tariffs.

"It's a lot more complicated to do that after IEEPA was struck down," Rachel Ziemba, adjunct senior fellow at the Center for a New American Security, told Al Jazeera. "There's no immediate policy lever and authorization that is available for the US to do that. So they need either an act of Congress or need to adapt some other trade tool, and there isn't really a national security-oriented trade tool."

Trump didn't name which countries would face his threatened tariffs, but the target is obvious: China and Russia have helped Iran build military capacity to counter US and Israeli pressure, supplying missiles, air defense systems, and technology. Both Beijing and Moscow have denied recent weapons shipments, though allegations against Russia persist.

An Empty Threat Aimed at China

Josh Lipsky, vice president at the Atlantic Council, said the threat is transparently directed at Beijing. "This is a China-related threat, the way I read it. And China will read it that way."

But Lipsky doesn't expect Trump to follow through—at least not before his planned mid-May trip to Beijing to meet with Chinese President Xi Jinping. "US tariffs on Chinese products have gone down a lot since the court ruling," said Ziemba, "and slapping on 50 percent tariffs now would be very expensive, especially for US importers and consumers."

Reuters has reported that Tehran was considering purchasing supersonic antiship cruise missiles from China, and in March reported that China's top semiconductor maker, SMIC, sent chipmaking tools to Iran's military, according to two senior Trump administration officials. Drone and missile parts routinely flow from Chinese entities to Iran, evading US sanctions.

"This is kind of an empty threat," Ziemba said, "but shows that when push comes to shove, Trump comes back to tariffs."

The Tariff Tools Trump Actually Has

Trump does have some active tariff mechanisms left over from his first term, including "Section 301" unfair trade practices tariffs on Chinese goods. He could potentially add duties to these, along with pending cases related to excess industrial capacity and China's compliance with a 2020 trade deal. But these would require a public notice period before taking effect.

He could also invoke Section 232 of the Cold War-era Trade Expansion Act of 1962, which allows sector-specific tariffs to protect strategic domestic industries on national security grounds. But that would require a new months-long investigation and public comments—hardly the "immediate" action Trump promised.

Russia, another source of arms technology for Iran, is already largely cut off from US trade following the 2022 invasion of Ukraine and resulting sanctions. US imports from Russia—one of the only countries not subject to Trump's now-cancelled "reciprocal" tariffs—jumped 26.1% to $3.8 billion in 2025, dominated by palladium for automotive catalytic converters, fertilizers, and enriched uranium for nuclear reactors. The Commerce Department is already moving to impose punitive tariffs on Russian palladium after an anti-dumping investigation.

The pattern is familiar: Trump announces sweeping tariff threats with no legal backing, creating market uncertainty and diplomatic chaos while ultimately lacking the authority to follow through. American importers and consumers would bear the cost of any tariffs he does manage to impose—not the foreign governments he claims to be punishing.