Queen's Policy Engagement


Northern Ireland’s Supreme Court Brexit Problem (and the UK’s too)

Professor Christopher McCrudden looks at the ramifications of the devolution issues of the recent Miller Case brought before the UK Supreme Court.

Northern Ireland’s Supreme Court Brexit Problem (and the UK’s too)

There are many unfortunate results of Brexit, but one of the most problematic is the adverse effects it has had on current and future relationships between Britain and Ireland, and within Northern Ireland. These adverse effects were entirely predictable and show little sign of abating, significantly contributing to the difficulties the UK government faces in unblocking the stalled negotiations.

In the story of what contributed to this deterioration, the UK Supreme Court’s failure to address head-on the adverse implications of triggering Brexit for devolution and the Belfast-Good Friday Agreement in the Miller case has attracted little comment in Britain, but is nevertheless of critical importance.

Just to remind you, the Miller case, brought by Gina Miller and other claimants, and decided by the Supreme Court in January 2017, considered the legality under UK law of the use of the royal prerogative to trigger Article 50 of the European Union and begin the process of the UK leaving the EU. The Miller case involved two constitutional questions of fundamental significance concerning the government’s claim to be able to use unfettered executive power under the royal prerogative to trigger Article 50.

The first question, and the one on which most comment has been forthcoming, concerned the implicit reversal, as a result of triggering Article 50, of the constitutional decision embodied in the European Communities Act (ECA) 1972 to join the EU (or the EEC, as it was in 1972). The Court insisted that any such change must be authorized by Parliament in primary legislation.

But there was a second issue, which most commentary has avoided considering in detail. This concerned the implicit reversal, also as a result of triggering Article 50, of constitutional decisions regarding the role of EU law in Northern Ireland and Scotland, embodied in the devolution acts and, as regards Northern Ireland, underpinning the Belfast-Good Friday Agreement.

Miller correctly provided a robust defence of Parliamentary authority in connection with the ECA 1972, and adopted a nuanced understanding of the constitutionally-grounded relationship between the UK and the EU, rejecting the government’s claim to unfettered executive power exercised under the royal prerogative. The way in which the Court decided the first issue was clearly correct, and we should applaud the Court’s bravery in facing down those in the tabloid press who would regard such displays of judicial independence as giving aid and succour to the “enemy”.

The major caveat to this generally favourable assessment of the Miller decision arises from what the Court did when it came to the second set of issues, what have been termed the ‘devolution issues’. In that context, the Court unfortunately proceeded to deploy a very traditional, and rather blunt, understanding of the principles of British constitutional law, including Parliamentary sovereignty. The devolution aspects of the Supreme Court’s judgment in Miller will come to be seen as a significant misstep, in that it failed to live up to the challenge of becoming a truly constitutional court for the UK as a whole.

This failure was particularly problematic for Northern Ireland, given the historical sensitivities and the instability of its government arrangements. Critically important questions of constitutional law were ignored entirely or decided in undue haste. The principal problems relate to the Court’s treatment of the British-Irish Agreement, an agreement underpinning the Good Friday Agreement and binding in international law, which was virtually ignored by the Court, and the unsatisfactory way in which the Court approached the Sewel Convention, which concerns the constitutional requirement that the government (if not Parliament) seek the consent of the Northern Ireland Assembly before effectively undoing the historic compromises in the Northern Ireland Act of 1998.

Indeed, the UK Supreme Court gave every indication that the devolution aspects of the litigation were a diversion from what it termed the “main” issue regarding the ECA 1972. In deciding the devolution issues, the Court drew on the most orthodox possible understanding of the principles of British constitutional law to override any more nuanced understanding of constitutional developments relating to Northern Ireland. No doubt, unintentionally, the Court adopted a view of the British constitution at odds with what is required to accommodate Northern Ireland’s evolving constitutional development, potentially undermining the Belfast-Good Friday Agreement.

The Court’s approach to the devolution arguments presented from Northern Ireland in Miller leave one to wonder whether much academic and political thinking in and about Northern Ireland on these issues is now fundamentally at odds with the understanding of the most senior members of the judiciary in the UK. That is not a healthy situation.

It is tempting to hope that if future litigation were to arise, in which the devolution issues arose in a different atmosphere, the Court might be persuaded to reconsider its approach towards the Northern Ireland devolution settlement. But, as things stand at the moment, traditional British constitutional orthodoxy seems ascendant, with significantly adverse effects for devolution and Northern Ireland’s constitutional developments, including the Belfast-Good Friday Agreement.

Most immediately, the Supreme Court’s approach has also exacerbated the UK’s Brexit negotiating difficulties in three important ways. First, by considering the devolution arguments raised in Miller as an afterthought, the Supreme Court encouraged Parliament and the government do so as well. Having happily triggered Article 50 with the quick blessing of Parliament, Theresa May is now stumbling through the devolution issues without proper guidance, let alone warning, from the UK’s highest court. A potential constitutional crisis is in the offing, further contributing to the sense in Brussels of a British government staggering from crisis to crisis.

Second, for the EU-27, Brexit in Northern Ireland involves not only domestic legal arrangements within the UK, but the (potential) breach of an existing international agreement between the UK and another EU Member State, Ireland. This has put the UK on the defensive, upping the Ireland/Northern Ireland issue to one of three issues on which “sufficient progress” must be made before future trade relationships can be negotiated.

Third, and most broadly, the Court’s heavy emphasis on the doctrine that Parliament can quickly do whatever it wants, signals to the EU-27 that any supposedly binding international agreements the UK enters into can be easily ignored by a future Parliament, without any domestic judicial remedy. This, in turn, has given special urgency in Brussels to the need to find creative ways in the Withdrawal Treaty can limit the ability of the UK to renege on future commitments – hence the standoff over the future role of the Court of Justice.

A necessary, but not sufficient, condition for future stability in Northern Ireland is a rethinking of the British constitutional underpinnings of the relationship between Britain and Ireland, one that explicitly transcends what appears to be the existing legal orthodoxy and tempers the doctrine of Parliamentary sovereignty (in the Northern Ireland context at least).

Doing so, sooner rather than later, would also signal a willingness to the EU-27 of the UK’s willingness to honour other commitments.  It would, of course, be an irony of the highest order if the clearest and most robust articulation by the Supreme Court of the fundamental nature of that doctrine was also the cause of its demise.


This article is based on Christopher McCrudden and Daniel Halberstam, “Miller and Northern Ireland: A Critical Constitutional Response,” UK Supreme Court Yearbook, Volume 8, 2017 (forthcoming). Available at SSRN. 

Daniel Halberstam is Eric Stein Collegiate Professor of Law, University of Michigan Law School; Director, European Legal Studies Program, University of Michigan Law School. He acted as a legal advisor to Agnew and others in the Miller case.


The featured image has been used courtesy of a Creative Commons license. 



Professor Christopher McCrudden
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Christopher McCrudden is Professor of Human Rights and Equality Law in the School of Law at Queen’s University Belfast, and William W Cook Global Professor of Law, University of Michigan Law School. He acted as junior counsel for Agnew and others in the Miller case.

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