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Litigation about Brexit continues to throw light on constitutional principles, both new and well-established. In the case of Wightman & others, petitioners  CSOH 61, advised on 8 June 2018, the Court of Session was called upon to consider whether the UK’s Article 50 notification could be unilaterally revoked by the UK in good faith such that the UK could continue to be a member of the European Union after 29 March 2019 on the same terms and conditions as it presently enjoys.
In refusing to make a reference to the Court of Justice of the European Union (“CJEU”) and dismissing the petition for judicial review, Lord Boyd considered the issue was hypothetical because there was in fact no suggestion the notification would be revoked. His Lordship also considered several aspects of Parliamentary privilege, and commented on the proper boundary between the legal and the political parts of constitutional process.
The issues in outline
In this application, all but one of the parties was an elected representative – a mix of members of the Scottish, UK and European Parliaments. The primary order sought was a reference to the CJEU in the following terms:
Does article 50 of the Treaty on European Union allow that the article 50(2) TEU notice which has been sent by the United Kingdom Government on behalf of the United Kingdom notifying the Council of the intention of the United Kingdom to withdraw from the EU can, while the United Kingdom remains a Member State, be revoked unilaterally by the United Kingdom in good faith and in accordance with its own constitutional requirements, such that the United Kingdom remains a Member State of the European Union on its existing terms of membership? 
The applicants contended that having an answer to this question was essential to their task as elected politicians. They wished to see the option of remaining in the EU considered along with the terms of any agreement between the EU and the UK; whereas, the current options were exiting the EU with or without such an agreement . It was argued for the applicants that while the government’s policy was that the Article 50 notice would not be withdrawn, it must be recognised government policy is subordinate to the sovereign Parliament. It followed that government could not restrict the choices which Parliament could make. Because individual Members of Parliament might consider that the better option is to reject the deal on offer and vote instead for the UK to revoke the Art 50 notice, and, it was said, thereby remain a member of the European Union on current terms. But it was a necessary prerequisite that the article 50 notification could be withdrawn, the only court or body that could give a definitive answer to that question was the CJEU .
In response, the Secretary of State for Exiting the EU argued that the application was hypothetical and academic. It was the government’s firm policy that the Article 50 notice would not be withdrawn, and, further, it had given a commitment to hold a ‘meaningful’ vote in Parliament on the withdrawal agreement and the terms of the UK’s future relations with the EU . In addition, the Secretary of State argued there was a fundamental issue about the competence of the application because Parliamentary privilege was clearly engaged.
Refusal to refer to CJEU
By the time Lord Boyd came to consider these arguments, the case had already been the subject of an appeal against refusal of permission to proceed, including adverse judicial comment about the formulation of the petitioners’ case. It is fair to say, that it was only the obvious constitutional importance of the issue which persuaded the Inner House of the Court Session to give permission to proceed at all.
In refusing to make a reference to the CJEU, and thereafter dismissing the petition on the basis that the central issue was hypothetical and academic, Lord Boyd noted there was no evidence that there is “a real and substantial prospect” of the UK government revoking the Article 50 notice of the UK’s intention to withdraw from the EU . Nor was there any suggestion that MPs were impeded from advocating remaining in the EU or the objective of securing an opportunity to vote for that option .
Revocation of the Article 50 notice was therefore contingent on a number of other factors being engaged for it to be a live possibility, and those could not be said to be realistically present. It followed that the issue raised in the petition was hypothetical . Even on the premise that there was an issue to refer, Lord Boyd was sceptical that the CJEU would accept a reference. The facts were not clearly established, nor would the European Council necessarily have reached a definitive position on revocation. It followed that in essence, the Court of Justice would also be faced with a hypothetical question .
Parliamentary privilege formed a central part of the argument, with the Secretary of State submitting that the question was at its heart about content and direction of Parliamentary proceedings, which are an aspect of Parliamentary privilege, and therefore not justiciable. As it was starkly put in argument, Parliamentary privilege goes to the jurisdiction of the court . This issue arose in part because the subject-matter of the proceedings plainly concerned a question which engaged current and future Parliamentary debate, and in part because the foundations of the petitioners’ case were ministerial statements about revocability of the UK’s Article 50 notice, because, it was said, the government had misdirected itself in law.
Part of the interest of this decision is the explicit engagement with several aspects of Parliamentary privilege – both in the sense of proceedings in one or other House, and at the level of principle in relation to separation of powers.
Of course, the separation of powers point has a long pedigree in this context (see Edinburgh & Dalkeith Railway v Wachaupe (1842) 8 Cl&F 710, Pickin v British Railways Board  AC 765, and Adams v Guardian Newspapers 2003 SC 425, paras 14 & 15). However the court concluded it was not necessary to explore the outer limits of its jurisdiction because the issue did not involve a proposed infringement of fundamental rights or freedoms. Rejecting a submission that referring to Parliamentary material did not impeach what was said or done in Parliament, Lord Boyd observed:
 It is of course true that the court is not being asked to rule on the validity of an Act of either the UK Parliament or Scottish Parliament. It is however being asked to settle a legal question raised by a number of MPs in the course of the legislative process. The petitioners seek judicial support for the option of the UK remaining in the European Union to be considered by Parliament. In my opinion that is a clear and dangerous encroachment on the sovereignty of Parliament. It is for Parliament itself to determine what options it considers in the process of withdrawing from the European Union. It is for Parliament to determine what advice, if any, it requires in the course of the legislative process.
Limits of legal intervention
One striking feature of the post-referendum constitutional environment has been the number of actual and projected challenges by means of litigation, sometimes supported by crowdfunding. In that context, the court in Wightman sounded a clear warning about the limits of such litigation, implicitly indicating that there are limits on the use of court process for political purposes – even where matters of constitutional moment are involved.
In the course of submissions for the petitioners, it had been argued that, in EU matters, “law trumped politics”. While that might be apt to convey the centrality to the EU order of the rule of law, the court held that care was necessary to avoid going further with the risk that becoming rule by the courts.
Politics requires space in which to flourish and the courts should only become involved when the elements of constitutional order require it (eg Miller) or to protect and uphold fundamental rights and freedoms. The court is not there to be used by one side or another to advance one side of a political debate. 
While the process that is Brexit has raised profound constitutional questions and has generated some innovative use of litigation, Wightman is a reminder of the limits of judicial process as a tool for constitutional action in the UK. As the court observed, the core issue is political, and its resolution is a political question which has ultimately to be debated and decided in Parliament and the country more widely.
Kenneth Campbell QC is an Advocate at Arnot Manderson Advocates, Edinburgh, a Barrister at Lamb Building, London and doctoral researcher at Edinburgh University Law School.
(Suggested citation: K. Campbell, ‘Wightman v Secretary of State: Article 50 and Parliamentary Privilege’, U.K. Const. L. Blog (22nd Jun. 2018) (available at https://ukconstitutionallaw.org/))