Deirdre Barnicle, Partner, McCann FitzGerald: On 20 February 2026, the US Supreme Court concluded that the US International Emergency Economic Powers Act (IEEPA) of 1977 does not allow the US President to impose tariffs; this power is reserved to Congress, and the ruling invalidated all tariffs imposed by President Trump under IEEPA on US trading partners e.g. the EU. Following this, on 4 March 2026, the US Court of International Trade confirmed that Customs and Border Protection (CBP) must issue refunds to the businesses who paid the illegal levies. However, the refund process remains unclear, and businesses are now burdened with the dual responsibility of navigating repayments while also preparing for incoming replacement tariffs.

Although the Supreme Court’s rejection of Trump’s tariffs may at first glance seem like a positive development, the President’s reaction and subsequent threat of further tariffs has brought significant uncertainty to the future of transatlantic trade. While CBP has announced the imposition of a 10% rate on all goods not covered by exemptions, Trump initially mooted a 15% tariff and it is feared that this threat of a higher rate will still come to fruition, following the US Treasury Secretary’s recent statement to that effect. The 10% tariff imposed under section 122 of the Trade Act of 1974 is a blunter instrument than the IEEPA - the Act requires measures to be ‘applied consistently’ to all countries and thus limits the possibility for carve-outs.

Moreover, there is a possibility that additional national security-related tariffs will be imposed under the Trade Expansion Act of 1962; these levies were not challenged in the court case and are thus unaffected by the Supreme Court’s ruling. If increased tariffs were levied against steel and aluminium, we can expect further consequences for transatlantic trade in this area. While the European Parliament’s Trade Committee has decided to suspend its work ratifying the EU-US tariff deal agreed with the Trump administration, as was observed by the European Parliament in its statement on the matter, the change of the US legal basis is unlikely to alleviate the economic impact of the tariffs on businesses and consumers; uncertainty is here to stay and the US still has many options for achieving the same results.

In the wake of the chaos, it is worth noting that it has been reported that nearly 85% of Irish goods exports to the US are still exempt and that the effective rate for Ireland is one of the lowest across OECD countries.

This article appeared in the March 2026 edition of the Irish Tax Monitor.