What now for Trump’s tariffs after the Supreme Court ruling?

The United States has entered a new phase of trade policy turbulence after the landmark Supreme Court decision last week invalidated President Trump’s use of the International Emergency Economic Powers Act (IEEPA) as a basis for sweeping global import tariffs.  

Within hours of that legal defeat, however, Trump responded by unveiling a new set of tariffs – a 10% global surcharge, swiftly raised to 15% – under alternative statutory authority.  

For UK importers and exporters, the ruling and the administration’s policy shift introduce both short-term uncertainty and significant strategic implications. 

In a six to three ruling, the Supreme Court held that the IEEPA does not authorise the President to impose broad import tariffs, effectively striking down most of the wide-ranging duties Trump had enacted using that law.  

Chief Justice Roberts wrote that while IEEPA allows the President to act in “unusual and extraordinary” national emergencies, it does not grant power to levy sweeping tariffs, a power the US Constitution reserves for Congress. 

This decision invalidated the majority of tariffs introduced in 2025, including Trump’s 10% reciprocal tariff on nearly all imports, as well as the additional duties linked to claims of drug-trafficking emergencies. Some sector-specific tariffs, such as Section 232 tariffs on steel, aluminium, autos and semiconductors, were left intact. 

The ruling also opens the door to significant refund liabilities. Analysts estimate that importers could seek refunds totalling over $130 billion, with processing expected to take 12–18 months. 

Within hours of the ruling, Trump invoked Section 122 of the Trade Act of 1974, a little-used provision allowing short-term import surcharges (up to 15%) to address balance of payments challenges. He announced a new 10% global tariff, effective almost immediately. 

The following day, he raised that tariff to 15%, claiming this was the maximum allowable rate under his newly chosen legal authority. 

Key characteristics of the new Section 122 tariff programme include: 

• A legal cap of 15%, which Trump has now reached  
• A limited 150-day duration, after which Congressional approval is required for extension  
• A broad scope covering most imports, with limited specific exemptions, such as critical minerals and certain food products 

This mechanism offers Trump narrower latitude than IEEPA but still constitutes a major escalation in tariff levels, particularly for partners previously operating under negotiated arrangements. 

Under the now invalidated IEEPA tariffs, UK goods, like those from most US trade partners, were subject to broad duties. Under IEEPA tariffs, UK goods typically faced a duty rate of 10%, but with some categories facing 15% tariffs or higher. EU countries faced 15%.  

With the IEEPA structure struck down, UK exporters could now see: 

• A flat 15% tariff applied across most product categories under the new Section 122 tariffs 
• Potentially lower tariffs for some categories than under prior IEEPA duties, depending on sector-specific rules that remain in place 
• Short-term uncertainty as trade investigations and potential additional tariff rounds continue 

Trump has signalled further action via Commerce Department probes. 

For UK importers sourcing from the US, the direct effect is limited, as these are US-applied tariffs. However, the policy turbulence may tighten transatlantic supply chains, influence pricing, and increase volatility in logistics and compliance planning. 

There are several issues for businesses to consider:  

• Tariff classification and valuation reviews –Frequent rate changes heighten the need for robust classification and valuation checks to avoid exposure to penalties by US Customs and Border Protection (CBP) 
• Refund opportunities under IEEPA tariff cancellations – Importers with US-destination supply chains should evaluate whether products previously entered under IEEPA tariffs are eligible for refund claims. The refunds are anticipated to be sizable but slow 
• Duty mitigation – Given the capped but broad nature of Section 122 tariffs, businesses should reassess long-term supply contracts and explore duty saving programmes such as US Foreign Trade Zones (FTZs), duty drawback, and, where legally feasible, origin engineering. All may yield meaningful savings 
• Trade agreement interactions – The UK has no dedicated trade deal with the US (merely a general framework agreed in May 2025, the UK-IS Economic Prosperity Deal. Consequently, UK exporters receive the same treatment as exporters from other countries. The new uniform tariffs add another layer to already challenging negotiations 

The Supreme Court’s ruling is fundamentally a reassertion of Congressional authority over tariff policy, but Trump’s swift pivot demonstrates that significant executive-driven tariff actions remain possible through other statutes. For UK traders, this creates: 

• Regulatory whiplash risk, since rapid shifts between legal regimes (IEEPA to Section 122) can disrupt pricing models and contract terms 
• Sector-specific unpredictability, because, while the global rate is now 15%, supplemental investigations could reimpose targeted tariffs 
• Competitive realignment, countries that formerly had negotiated the impact of IEEPA tariffs (such as Japan and the EU) may actually benefit from a lower uniform tariff under the new system, altering relative UK competitiveness 

For UK exporters and importers, the critical task is to stay agile: monitor evolving tariff announcements, prepare for compliance recalibration, and evaluate duty mitigation strategies. While the 15% global tariff is currently capped and time limited, further shifts are possible – and likely – given the administration’s publicly stated intentions. 

Approval code: NTEH7022607