The United Kingdom’s Constitution and Brexit: A ‘Constitutional Moment’?

9 Pages Posted: 27 May 2020 Last revised: 28 May 2020

See all articles by Mark Elliott

Mark Elliott

University of Cambridge - Faculty of Law

Date Written: May 25, 2020


The United Kingdom’s constitution is, by any reasonable standard, an unusual one. The reason for this, it is sometimes said, is that the UK’s constitution is an evolutive one that has developed incrementally over a long period of time, rather than the product of the sort of a defining ‘constitutional moment’ that, in many countries, supplies the supplies the foundation upon which (new) constitutional arrangements are built. This is not, however, strictly true. The UK undoubtedly experienced a highly significant constitutional moment in the late 17th century, when the fundamental principle was established that the Crown in Parliament enjoys legislative supremacy, thus giving rise to the axiomatic concept of parliamentary sovereignty. However, while these events, which reached their denouement in 1688-9, doubtless amounted to a constitutional moment, what is unusual — and what sets the UK constitution apart from nearly all others — is that that critical moment was not followed by any recognisable form of codification. In this way, the near-uniqueness of the UK’s constitutional arrangements is attributable not to the want of any significant constitutional moment in the UK’s long constitutional history, but to the absence of any attempt to codify the implications of such a moment. That lack of codification certainly does not, however, detract from the defining significance of what happened in the late 1600s, whereby parliamentary authority was established at the expense of monarchical power.

More than 300 years later, the question arises whether the UK is currently experiencing another constitutional moment which, questions of codification aside, might prove to be as significant an inflection point in the UK’s constitutional history as the events that unfolded in the 1680s. The occasion for asking that question is provided by the UK’s departure from the European Union, which occurred on 31 January 2020. This is so for two reasons. First, withdrawal from the EU was a highly significant constitutional — and well as social, economic and political — development, the repercussions of which will be felt for a very long time to come. Second, however, Brexit is the antithesis of a self-contained phenomenon in constitutional — as in other — terms. As well as being a consequential constitutional event in its own right, Brexit is likely to yield, and in some respects is already producing, substantial reverberations within the wider constitutional order. Against this background, the purpose of this article is to sketch the existing and likely constitutional implications of Brexit for the UK and, in doing so, to assess whether the UK is currently experiencing what history might come to regard as a constitutional moment or inflection point.

Keywords: constitutional law, European Union law, UK law, United Kingdom constitution, Brexit

Suggested Citation

Elliott, Mark C., The United Kingdom’s Constitution and Brexit: A ‘Constitutional Moment’? (May 25, 2020). [2020] Horitsu Jiho 15–22, University of Cambridge Faculty of Law Research Paper No. 22/2020, Available at SSRN:

Mark C. Elliott (Contact Author)

University of Cambridge - Faculty of Law ( email )

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Cambridge, CB3 9DZ
United Kingdom

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