Finger on the trigger

12 October 2016

Does triggering Art 50 require a prior Act of Parliament, asks Michael Zander QC

  • This week marks the beginning of the court case to determine if Parliament’s approval in a statute is required to trigger Art 50 of the Treaty on European Union to officially start the Brexit process.

The Prime Minister, Theresa May, has said she intends to begin the process of withdrawal from the EU by triggering Art 50 of the Treaty on European Union without putting the matter before Parliament. Legal action seeking a declaration that such action would be constitutionally unlawful will be heard this week by the Divisional Court, Lord Thomas, Lord Chief Justice, presiding. The case is listed for argument on 13, 17 and 18 October. 

The claimants’ case

The various claimants are private individuals. The so-called lead claimants, represented by Mischcon de Reya, have three QCs led by Lord Pannick. The so-called “People’s Challenge Group”, represented by Bindmans, have two QCs led by Helen Mountfield.

The People’s Challenge team relies on crowdfunding.

The claimants say that no constitutionally valid decision to leave the EU has yet been taken. As MPs were informed at the time, the referendum was merely consultative: “This Bill requires a referendum to be held on the question of the UK’s continued membership of the EU before the end of 2017. It does not contain any requirement for the UK government to implement the results of the referendum, nor set a time limit by which a vote to leave the EU should be implemented. Instead, this is a type of referendum known as pre-legislative or consultative, which enables the electorate to voice an opinion which then influences the government in its policy decisions. The referendums held in Scotland, Wales and Northern Ireland in 1997 and 1998 are examples of this type, where opinion was tested before legislation was introduced. The UK does not have constitutional provisions which would require the results of a referendum to be implemented, unlike, for example, the Republic of Ireland, where the circumstances in which a binding referendum should be held are set out in its constitution.” (House of Commons Library Briefing Paper on the European Union Referendum Bill 2015-16, No.07212, 3 June 2015, p 25)

The claimants argue that the decision to leave the EU cannot be made by the executive through exercise of the Royal Prerogative. It requires an Act of Parliament. The argument is based on three related but independent propositions:

  • Prerogative power to decide that the UK should leave the EU has been implicitly abrogated by domestic statutory provisions. 
  • If any prerogative power still subsists in this field, it does not extend to abrogating or removing fundamental rights, in particular citizenship rights which can only be done by a statute. Nor can the prerogative be used to pre-empt Parliament’s decision as to whether to continue with a statutory scheme.
  • Abrogating or removing fundamental rights derived from EU membership without statutory authority would be an abuse of prerogative power. 

The three propositions are not cumulative. If any is accepted the claimants would win. 

Different views have been expressed as to whether notification to leave the EU through activation of Art 50 could later be withdrawn without the unanimous consent of all the 27 other member states. The claimants submit that the court should therefore proceed on the assumption that once Art 50 is triggered, the UK’s exit from the EU in practice is irreversible. 

The claimants argue that since in the European Communities Act 1972 Parliament legislated to enlarge the EU (as it now is) to include the UK by transporting the rights conferred by the EU into UK law, it was now for Parliament to legislate to contract the EU legal order by removing the UK. They cite cases in which the courts assumed that an Act of Parliament would be necessary before the UK could repudiate the EU Treaties: Blackburn v AG [1971] 2 All ER 1380, [1971] 1 WLR 1037, per Denning LJ; Macarthys Ltd v Smith  [1979] IRLR 316, [1979] 3 All ER 325 per Lord Denning; R (Shindler) v Chancellor of the Duchy of Lancaster [2016] EWCA 469 per Lord Dyson; Pham v Secretary of Stater for the Home Department [2015] UKSC 19, [2015] 3 All ER 1015, per Lord Mance.)

It is established that the prerogative power cannot be exercised in a field that Parliament has “occupied” by enacting legislation. A field can be occupied by express words or by “necessary implication”. 

In EU matters, the claimants argue, the prerogative power has been abrogated by statutory provisions which confer rights from and under the EU Treaties on UK citizens; and/or expressly require a continuing statutory basis for directly applicable or directly effective EU law; and/or depend upon, or assume, the UK’s continued membership of the EU. A notification under Art.50 without legislative authority, they argue, would “frustrate or substantially undermine” the terms of the 1972 European Communities Act. 

They draw also on the European Union Act 2011, Pt I of which precludes the executive from ratifying any treaty which amends or replaces the EU Treaties without both a referendum and an act of parliament permitting it. In introducing the Bill in the Commons, William Hague, the then Foreign Secretary, said: “It is the most important change since we joined what was then called the European Economic Community. It marks a fundamental shift in power from Ministers of the Crown to Parliament and the voters themselves.” A purported exercise of prerogative power to withdraw from the EU would cut across Parliament’s intention as expressed in the 2011 Act. 

The devolution legislation for Scotland, Wales and Northern Ireland is another leg of the claimants’ argument. That legislation, they say, was predicated on the application of EU law, thereby protecting the EU rights of citizens of the devolved nations. In addition, under the Good Friday Agreement, the governance of Northern Ireland and the relationship between the UK government, Northern Ireland and the Irish Republic was predicated on the UK’s continuing EU membership. Given the role of EU law in these legislative arrangements, the use of the prerogative to withdraw from the EU was precluded by necessary implication. The courts should be particularly slow to find that the Royal Prerogative may be relied on in a manner cutting across primary legislation that had particular constitutional significance and status.

Whatever its extent, the claimants argue, the prerogative power cannot be used to modify or remove the rights of UK citizens, in particular fundamental rights derived from citizenship or directly enforceable private law rights derived from the European Treaties.

In Rayner (Mincing Lane) Ltd v DOT [1990] 2 AC 418, [1989] 3 All ER 523 Lord Oliver said: “The Royal Prerogative, whilst it embraces the making of treaties, does not extend to altering the law or conferring rights upon individuals or depriving individuals of rights which they enjoy in domestic law without the intervention of Parliament.”

A crucial issue will be how the Art 50 notification should be regarded. The government will contend that it does no more than notify. The claimants will argue that in reality it has serious effects and that the court should have regard to the substance not the form. Lawton LJ said in Laker Airways v Department of Trade [1977] QB 643, [1977] 2 All ER 182: “[T]he Secretary of State cannot use the Queen’s prerogative powers in this sphere in such a way as to take away the rights of citizens…By withdrawing designation this is what in reality, if not in form, he is doing.” The government’s claim that notification under Art 50 did not affect rights was to ignore the reality. 

The rule that the prerogative may not be relied upon to deprive citizens of their right was an aspect of the principle of legality. Such rights may only be removed by express statutory authority: “Where rights have been conferred under statute, and would be removed or diminished by a decision to leave the EU (which, pursuant to Art 50, is self-executing), the principle of legality prevents these rights from being restricted or removed. What it requires is that any such restriction or removal of statutory rights must be done by Parliament squarely confronting what it is doing by the use of express words, and accepting the political cost. It cannot be done by the executive, purporting to exercise its untrammelled executive power.” (Skeleton Argument of the Second Group of Interested Parties, para.69)

The government’s case

The government’s argument is that giving notice under Art 50 is an administrative act on the international plane within the executive’s power. Notification would be based on the decision to leave the EU “as articulated in the referendum result”. “The basis on which the referendum was undertaken was that the government would give effect to the result of the referendum. That was the basis on which the people voted. The 2015 Act neither expressly nor implicitly required that further Parliamentary authority would be required before an Art 50(2) notification could be given to commence the process of giving effect to the outcome of the referendum” (Government Skeleton Argument, para 8(1)).


  • The decision to leave the EU is not justiciable. 
  • The relief sought in the claim is “constitutionally impermissible” in that the court would be requiring the secretary of state to introduce legislation to give effect to the outcome of the referendum and thereby be trespassing on proceedings in Parliament.
  • If the claim is justiciable and within the proper bounds of the court’s role, the exercise by the Crown of its prerogative power is consistent with domestic constitutional law. It is not precluded by or inconsistent with the European Communities Act 1972. Nor would the commencement of the process of withdrawal from the EU change any common law or statute. That would be a matter of future negotiations, Parliamentary scrutiny and implementation by legislation.

The government’s case will be opened by the Attorney-General, Jeremy Wright QC. 

Whatever the result, the case will be leap-frogged to the Supreme Court for a hearing already scheduled for December.

Michael Zander QC is Emeritus Professor, LSE


Legal disputes boutique grows the partnership with promotion

Restructuring partner joins in London

Medical negligence expert appointed chief assessor of clinical negligence panel