Supreme Court Strikes Down IEEPA Tariffs 6-3 — Cross-Border Trade Regime Enters New Legal Chapter

The US Supreme Court ruled 6-3 in Learning Resources, Inc. v. Trump that the International Emergency Economic Powers Act does not authorise presidential tariffs, voiding an estimated $166 billion in duties collected from over 330,000 businesses. The S&P 500 rose 0.69% to 6,909.51, the Dow gained 230 points to 49,625.97, and the Nasdaq added 0.9% to 22,886.07 as markets initially cheered the ruling.

Within hours, Trump signed a Proclamation under Section 122 of the Trade Act, imposing a 10% "temporary import surcharge" on all countries effective February 24, with a 150-day sunset clause expiring July 24 unless extended by Congress. The net effect: unilateral presidential trade powers have narrowed, but the tariff confrontation continues through different legal channels.

For cross-border investors and multinational supply chains, the ruling fundamentally changes the risk calculus. Trade policy becomes slower and more procedurally constrained — reducing headline volatility but increasing the importance of Congressional dynamics and judicial precedent. Companies with US import exposure should model for a 10–15% baseline tariff on most goods under Section 122, with sector-specific rates of 25–50% persisting through Sections 301 and 232 for strategic industries. The shift from executive emergency powers to statutory authorities means trade disputes will play out over quarters rather than tweets — favouring firms with patient capital and adaptable supply chain structures over those dependent on just-in-time cost optimisation.