Brexit: Foundational Constitutional and Interpretive Principles: I

Paul Craig - 27th October 2016

The post-referendum discourse has been marked by vibrant political and legal exchange in Parliament and the courts. This is not the place for detailed engagement with all such arguments, nor is it the intent of this contribution. To the contrary, it is to stand back from that discourse and highlight some important constitutional principles that pertain to Parliament’s voice in the forthcoming Brexit negotiations, and also some foundational interpretive principles that have been lost sight of in the debate concerning Article 50. There are, as will be apparent, connections between the two sets of issues. The former will be dealt with in this blog, the latter in the blog that follows.

The Supreme Court will ultimately decide whether Parliament has a legal right for its voice to be heard prior to the triggering of Article 50. This piece is however focused on the twin constitutional principles that pertain in this area, irrespective of the outcome of this litigation. They are simple, but in danger of being lost sight of or diluted in the political forum.

The first is that the UK’s constitutional cornerstone is parliamentary sovereignty, it is manifestly not sovereignty of the executive or the government. In political terms Parliament has only recently been active and demanded some real voice prior to the triggering of Article 50. Many, myself included, welcome this development. It is constitutionally right and proper, and there is no warrant for denying this on the ground that it would thereby unduly hamper the government in its negotiation. There is a middle way between Parliament seeking to micromanage the negotiations, and being presented with a done deal by the executive with no room for choice. This is more especially so, since the outcome of the referendum was indeterminate as to what kind of withdrawal deal should be struck by the UK.  The constitutional implications of this are stark and simple. If a parliamentary majority were to be secured for the passage of legislation that would require an affirmative vote prior to the Article 50 trigger this would be entirely constitutionally legitimate, irrespective of whether it chimed with the views of the executive; it would also be constitutionally legitimate for Parliament in such legislation to structure the direction of the negotiation, and/or to specify regular ‘reporting lines’ from the executive back to Parliament.

The second constitutional principle concerns the ‘back end’ of the negotiating process. During litigation in the High Court counsel for the government conceded under questioning that it was ‘highly likely’ that the government would accept that there should be a vote on the withdrawal agreement prior to its ratification. This was wise, but the tone of grace and favour is nonetheless misleading. The Constitutional Reform and Governance Act 2010 enshrines the constitutional principle that the executive cannot bind the UK at the international level if the House of Commons disapproves of the putative deal. It might be argued that the tone of concession was warranted because the 2010 legislation does not in terms guarantee a full debate and conclusory vote, this still being in the gift of the government. This is, however, to ignore the detailed provisions of the 2010 legislation, which clearly show that Parliament was intended to have this more extensive involvement whenever there was any amendment to the EU treaties, and this should a fortiori be so where the UK is contemplating something even more significant, viz leaving the EU. The response of committed Brexiteers to this tends to be dismissive, their argument being that any such negative vote could not in any event prevent exit, but would merely mean that the UK fell off the edge of the cliff at the end of two years with whatever the default position might be under the WTO rules. This conclusion is itself predicated on the assumption that Article 50 is irrevocable once triggered. That raises the interpretive fundamentals, which will be considered in the next blog.

Author profile

Paul Craig, MA 1973, BCL 1974, Oxon, Gibbs Prize 1972, Henriques Prize 1973, Vinerian Scholar 1974. Professor in English Law since Oct 1998- St. John's College. Formerly: Professor in Law 1996-1998 Worcester College; Lecturer, Magdalen College, 1974-75, Reader 1991-96.


Paul Craig “Brexit: Foundational Constitutional and Interpretive Principles: I” (OxHRH Blog, 27 October 2016) <> [Date of Access]


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