Dillon judgment and withdrawal agreement tensions

The UK Supreme Court’s Dillon judgment in May 2026 casts doubt on the implementation of the UK’s commitments under the UK-EU Withdrawal Agreement. This is a decision that informs not only our understanding of the Court’s approach to EU law issues after Brexit, but also its approach to rights issues. It also has the potential to generate a new flashpoint in UK-EU relations.

As part of the Windsor Framework, which provides the special arrangements for Northern Ireland within the Brexit deal, the UK committed in Article 2 to ensuring that, insofar as EU law was relevant to the Rights, Safeguards and Equality of Opportunity (RSEO) Chapter of the Belfast/Good Friday Agreement of 1998, it would ensure no diminution of EU law protections following Brexit. It also made specific pledges with regard to key anti-discrimination provisions of EU law within Annex 1 (these were not raised by the facts in Dillon). Together, these commitments provided a higher baseline of rights and equality protections in Northern Ireland than in other parts of the UK, where Article 2 does not apply.

Significance of Article 2

Article 2 was a significant commitment within the Brexit deal, because the UK Government could not have maintained that Brexit complied with its 1998 Agreement obligations without it. EU law underpinned many of the commitments being made in 1998, particularly towards anti-discrimination law. In August 2020, during the Brexit deal’s implementation period, the Northern Ireland Office asserted that this commitment could provide a basis for litigation and covered a range of EU measures, including a specific reference to the Victims’ Directive. When litigants attempted to rely on these commitments, however, the UK Government (under both the Conservatives and Labour), have sought to deny their binding legal effect.

The Dillon litigation concerned the controversial Northern Ireland Troubles (Legacy and Reconciliation) Act 2023 and in particular, when it comes to the Windsor Framework, its immunity provisions, which shuttered existing cases and prevented civil and criminal liability in relation to activity connected with the Northern Ireland conflict. There are multiple aspects of this litigation, including ECHR claims but, for the purposes of this article, under Windsor Framework Article 2 the applicants challenged the compatibility of these arrangements with Articles 11 and 16 of the Victims’ Directive, which provides victims of crime the ability to challenge refusals of the authorities to prosecute.

Domestic courts and the Legacy Act

When the Northern Ireland Court of Appeal found that that the Legacy Act breached the UK’s Windsor Framework commitments, it did so on the basis of the preservation of litigable EU rights protections for Northern Ireland under Article 2 of the Windsor Framework, and the express commitments towards the Victims’ Directive made by the UK Government in its August 2020 Explainer. The Labour Government was notably committed, in its 2024 manifesto, to removing the amnesty provisions from the previous government’s legacy legislation. Even though it is pursuing those legislative reforms, the Labour Government still pursued an appeal before the UK Supreme Court.

This is a strange situation, in which Dillon became an appeal with little obvious legal purpose when it comes to the legislation in question. It was nonetheless mounted because the UK Government was concerned about the wider implications of the Windsor Framework commitments for its law and policy making. Having made far-reaching promises with regard to one part of the UK, which had implications for policies touching upon rights which were intended to be applicable across the UK, the Government was hoping that the Supreme Court would relieve them of the impact of these obligations.

In Dillon, the Supreme Court did not deny that binding obligations for the UK, actionable in domestic court, would result in ‘certain circumstances’ from the terms of Article 2 (para 120). Whatever the UK Government might have wanted the outcome of this case to be, contrary suggestions flew in the face of not only the language of Article 2 but also of Westminster’s implementing legislation, which indicated that it could provide the basis for legal action.

Restrictive interpretation of Article 2

In accepting the UK Government’s appeal, however, the Supreme Court adopted a number of positions which have the effect of severely restricting the operation of Article 2 in a wide range of cases. It asserted that the EU rules of direct effect apply to the reading of the 1998 Agreement, even though it is not an EU measure, but rather a separate international agreement being referred to in the Withdrawal Agreement. In doing so, the Court has restricted the extent to which the rights chapter of the 1998 Agreement can sustain litigation; the specific bullet-point list of rights and equality protections under the RSEO chapter of the 1998 Agreement meets the certainty requirements of direct effect, the broader commitment to the ‘civil and religious rights of everyone in the community’ does not (para 118).

The Court also adopted a restrictive reading of the requirements of the Victims’ Directive and the application of the Charter of Fundamental Rights. Even when it came to the bullet point list, the Court suggested that it would regard these as being applicable insofar as they related to the ‘communal conflict’ in Northern Ireland (para 119). In short, the outline of the Article 2 commitment has been preserved, but the tests around it are asserted in such stringent terms that it becomes very difficult to advance litigation in practice. The obligation might still look inviting for litigants, but its practical protections have been hollowed out. That much of the Court’s discussion, beyond the specific position that there was no connection between the Victims’ Directive and the elements of the RSEO chapter that the Court was willing to recognise as having direct effect, amounts to obiter dicta and only contributes to the uncertainty for litigants that the decision generates.

International law implications and dispute mechanisms

The Supreme Court is not, moreover, the final forum for determining the UK’s Withdrawal Agreement obligations, and indeed a domestic court judgment can be the source of a breach of international obligations. The EU has repeatedly affirmed the importance of its commitments towards Northern Ireland and the role of EU law in sustaining the RSEO chapter. The Withdrawal Agreement sets out, in Articles 165-169, the process by which putative breaches can be challenged through its committee structures and ultimately through arbitration if mutual agreement cannot be reached. If there are any EU law issues at stake within that process, then under Articles 170-174 they must be referred by arbitrators to the Court of Justice of the European Union (CJEU) for authoritative determination (in the context of Dillon, this could encompass the scope of the Victims’ Directive, the application of direct effect and the court’s treatment of the EU Charter of Fundamental Rights). Once that authoritative ruling has been issued, then the arbitrators would apply that CJEU’s outcomes and determine the non-EU law questions (which would require them to address the correct reading of the scope of the RSEO chapter and the significance of the 2020 Explainer pledges) and issue a determination.

The Dillon judgment calls into question a significant element of the UK’s Withdrawal Agreement commitments. Domestic litigation will continue to contest these constraints, while the EU Commission will come under pressure to challenge these issues within the Withdrawal Agreement’s committee framework and could ultimately pursue arbitration against the UK if the UK Government refuses to address the breach. These challenges will test whether the rhetoric surrounding the 1998 Agreement, so prominent during the Brexit debates, carries any real weight.