In a landmark ruling with global trade implications, a US federal trade court has blocked former President Donald Trump's sweeping tariffs, stating he overstepped his authority by imposing blanket duties on imports from countries running trade surpluses with the United States.

The Court of International Trade ruled that while Congress has exclusive constitutional authority to regulate foreign commerce, that power cannot be bypassed by presidential emergency measures.

“The use of tariffs in this manner is impermissible,” the panel of judges wrote, clarifying that the decision was based on legal limits—not on whether the policy was wise or effective.

The ruling is a significant blow to Mr Trump’s trade strategy, which had made aggressive tariff use a centrepiece of his campaign to reduce the US trade deficit, revive manufacturing, and pressure trading partners into new deals.

The tariffs, ranging from 10% to 54%, were enacted under the International Emergency Economic Powers Act (IEEPA), a law typically used for sanctions and financial freezes—not for trade restrictions.

The Trump administration quickly filed an appeal, challenging the court’s authority.

A White House spokesperson defended the tariffs, calling the US trade imbalance “a national emergency” that has hurt American workers and industries, and criticised the court for interfering in presidential powers.

The decision emerged from two lawsuits—one filed by a group of small US importers, the other by 13 states, including Oregon.

Plaintiffs argued the tariffs would harm their operations and drive up costs.

The court agreed, stating that the tariffs were unlawful for all, not just the plaintiffs.

At least five other legal challenges remain pending.

Financial markets reacted positively to the ruling.

The US dollar strengthened, especially against the euro and yen, while Wall Street futures and Asian equities saw gains.

If upheld, the decision could dismantle one of Trump’s key economic tools and shift future administrations back toward more conventional trade negotiations and investigations.

Legal experts note this may also curb the use of IEEPA for broad economic actions unrelated to national security threats.

For Irish businesses and exporters, the ruling signals a more stable and predictable US trade environment—at least for now.

The path forward will depend on the outcome of the appeal, which could reach the US Supreme Court in due course.