What legal mechanisms allow the UK or EU to sanction a close ally like the US?

1. Legal authority: domestic statutes versus EU secondary law

The UK’s principal domestic authority is the Sanctions and Anti‑Money Laundering Act 2018, which underpins UK regulations and the consolidated UK sanctions list maintained by government agencies and OFSI ^[1]. The EU operates through Council regulations and successive “sanctions packages” — amendments to instruments such as Regulation 833/2014 and Regulation 269/2014 — that bind member states and create a single legal regime across the bloc ^{[2] [3]}.

2. How those rules actually target allies in practice

Both systems are designed to be targeted: they list individuals, entities or sectors for asset freezes, trade restrictions, travel bans and export controls. The UK maintains a public sanctions list and issues general licences and wind‑down periods (for example in sanctions on Russian energy firms) so measures can be phased in without immediate market chaos ^{[1] [3]}. The EU’s packages similarly specify sectors and named targets and can be broadened or narrowed through subsequent Council decisions ^[2].

3. Can the UK or EU sanction a “close ally” such as the US?

Legally, domestic and EU frameworks do not contain an explicit “friend or foe” immunity: measures apply to persons or activities meeting the statutory criteria, regardless of nationality, and can in theory be directed at partners if the legal thresholds are met. Available sources document frequent coordination with the US but show the UK and EU act independently and have imposed measures that diverge from US policy when their legal or political tests required it ^{[2] [4]}. Sources do not discuss a concrete recent case of UK/EU sanctions targeted at the United States itself; available sources do not mention a UK/EU sanctioning the US (not found in current reporting).

4. Practical and political constraints on sanctioning an ally

The sources emphasise coordination and political reality: sanctions are instruments of foreign policy used to deter behaviour or coerce change, and the UK/EU typically align with partners for collective impact ^[4]. Practical constraints include the economic interdependence with allies, the reciprocal risk of secondary measures or tariffs, and the political cost within domestic institutions and international fora — factors that make sanctioning a close partner unlikely even if legally possible ^{[4] [2]}.

5. Tools beyond designation: export controls and secondary measures

The UK and EU can deploy export controls, sectoral restrictions and anti‑circumvention rules as adjuncts to person‑based listings. Recent EU/UK packages targeted Russia’s energy sector with export bans, shipping/insurance controls and tightened rules to block circumvention through third countries ^{[2] [3]}. These instruments can have wide economic effects and be used selectively against non‑state actors or companies associated with a state’s policies rather than states per se ^[3].

6. Coordination with — and limits vis‑à‑vis — US measures

The record shows frequent trilateral alignment on major targets (e.g., coordinated action on Russian oil majors in October 2025), but also divergent approaches and timing; the US often relies on executive orders and OFAC designations while the EU uses Council regulations and the UK uses domestic regulations under the Sanctions Act ^{[3] [1]}. Sources show cooperation (memoranda of understanding between OFAC and OFSI) while noting occasional policy divergence and delays in coordination ^{[5] [4]}.

7. Legal safeguards and enforcement mechanics

Sanctions regimes include legal safeguards: public lists, statements of reasons, and the possibility of judicial challenge (examples in reporting on relisting challenges in EU courts), and authorities issue licences and FAQs to manage compliance and wind‑downs ^{[6] [1]}. Enforcement is administered by specialist agencies (OFSI in the UK; EU competent bodies), and non‑compliance can trigger criminal and civil penalties — though implementation differs between jurisdictions ^{[1] [7]}.

8. Bottom line — law permits, politics restrains

Legally, the UK and EU have the mechanics to sanction any qualifying person or entity, and their toolboxes include asset freezes, travel bans, export controls and targeted sectoral measures ^{[1] [2]}. In practice, political considerations, economic interdependence and alliance management strongly discourage using those tools against major partners like the US; the sources show cooperation and occasional divergence, not mutual sanctioning between close allies ^{[3] [4]}.