Supreme Court rules some Trump tariffs unlawful in 6-3 decision

The U.S. Supreme Court has struck down key elements of former President Donald Trump’s tariff regime, ruling that the International Emergency Economic Powers Act (IEEPA) does not authorize the president to impose broad import duties without explicit congressional approval. The 6-3 decision could have implications for industries — including the water sector — that rely on global supply chains for treatment chemicals, equipment and infrastructure materials.

Chief Justice John Roberts, writing for the majority, said that IEEPA “does not” grant tariff authority, noting that Congress must clearly authorize broad economic actions such as tariffs. The Court applied the “major questions doctrine,” which holds that executive actions with wide economic impact require unambiguous legislative backing.

While the ruling primarily addresses tariffs that were imposed under emergency powers, it invalidates many of the sweeping global tariffs Trump enacted in 2025 and may leave room for other tariff categories imposed under different statutes — such as Section 232 national security tariffs — to remain in force.