In January 2017 the Supreme Court held that ministers needed an Act of Parliament before they could give notice of the United Kingdom’s intention to leave the EU under article 50. The referendum had produced a political mandate to leave. The legal question was who had authority to take the step that, on the assumptions before the Court, would lead to changes in domestic law.
The United Kingdom joined the European Economic Community on 1 January 1973. The European Communities Act 1972 gave European law effect in domestic law. In the European Union Referendum Act 2015, Parliament provided for a referendum but not for the legal consequences of either result. On 23 June 2016 a majority voted to leave, and ministers intended to notify the European Council under article 50(2) by the end of March 2017. Article 50 permits withdrawal only in accordance with the member state’s own constitutional requirements. After notice, the Treaties cease to apply when a withdrawal agreement takes effect or, failing that, two years after notification, unless that period is unanimously extended. The Court was not deciding whether leaving was wise, or what the terms should be. The legal question was whether ministers could give notice by prerogative alone.
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How the issue reached the Court
Gina Miller and Deir dos Santos succeeded in the Divisional Court. On 3 November 2016 Lord Thomas of Cwmgiedd LCJ, Sir Terence Etherton MR and Sales LJ held that statutory authority was required. The Secretary of State for Exiting the European Union appealed. In Northern Ireland, Maguire J had rejected arguments advanced by Steven Agnew and others and by Raymond McCord, and questions from those proceedings were referred to the Supreme Court. The Lord Advocate and the Counsel General for Wales supported a statutory requirement and relied on the Sewel Convention. The Attorney General for Northern Ireland supported the Secretary of State.
Why the prerogative was not enough
Ministers may normally make and end treaties without an Act of Parliament. Under the United Kingdom’s dualist constitution, a treaty binds the state internationally but does not itself change domestic law. Unless statute allows it, ministers also cannot use the prerogative to change domestic law or frustrate a statute.
The majority — Lord Neuberger, Lady Hale, Lord Mance, Lord Kerr, Lord Clarke, Lord Wilson, Lord Sumption and Lord Hodge — held that the 1972 Act did more than copy existing treaty rules into a statute. Section 2(1) requires rights and obligations arising under the EU Treaties from time to time to be recognised and enforced so far as the Treaties require that without further enactment. Section 2(2) permits implementing regulations. A new treaty becomes one of the EU Treaties for these purposes only if Parliament adds it to section 1(2). While the 1972 Act remains in force, EU law is, through that Act, an independent and overriding source of domestic law. The majority adopted the image of the Act as a conduit pipe. Parliament can repeal the Act, but until it does, legislation inconsistent with EU law is to that extent ineffective. Legislation altering the domestic constitutional status of EU law is different, because Parliamentary sovereignty remains fundamental.
The Secretary of State argued that section 2 merely tracks obligations for so long as the Treaties apply, so Parliament had already accepted that ministers could withdraw. The majority agreed that the content of EU law can vary without a fresh Act, and that section 2 was not meant to keep importing EU law after the United Kingdom had ceased to be bound. They did not accept that ministers could bring that situation about. A change in EU law flowing through the conduit is different in kind from removing the source by withdrawal. That would be a fundamental constitutional change, and it would occur even if Parliament never repealed the 1972 Act. Some domestic rights enjoyed through EU law would be lost. The Divisional Court’s first category, rights capable of replication in United Kingdom law, was enough; rights enjoyed in other member states and rights to participate in EU institutions did not need to be decided.
The long title, concerned with enlargement, and the Act’s controls on new and ancillary treaties also pointed away from a ministerial power to reduce domestic EU law to nothing. A power of withdrawal was not itself a right to be given legal effect or enjoyed in the United Kingdom under section 2. Because the EU Treaties are a source of domestic law, the treaty prerogative could not be used to leave them unless the 1972 Act positively created that power. It did not.
It would be inconsistent with long-standing and fundamental principle for such a far-reaching change to the UK constitutional arrangements to be brought about by ministerial decision or ministerial action alone.
The parties agreed, and the Court assumed without deciding, that notice cannot be conditional and cannot be withdrawn once given. On that footing, notice would start an irreversible process before Parliament had authorised the change. Ministers’ proposed Great Repeal Bill could not be treated as law already made.
Later legislation and the referendum
Article 50 conferred no domestic authority to give notice, because it returns the question to domestic constitutional requirements. Adding the Lisbon Treaty to the 1972 Act did not decide whether those requirements included a statute. The 2008 and 2011 Acts restricted particular EU decisions, including a ministerial vote under article 50(3) on extending another state’s withdrawal period, but created no prerogative power to give notice under article 50(2). The majority held that no such power had ever existed and therefore none was reinstated by silence. Unlike some other referendum statutes, the 2015 Act specified no legal consequence of the vote. The Commons resolution of 7 December 2016, calling for notice by 31 March 2017, was politically important but was not an Act. Until Parliament legislated, the referendum’s force was political rather than legal.
Devolution and the Sewel Convention
The devolution statutes constrain devolved institutions from breaching EU law and assume membership, but they do not require the United Kingdom to remain a member. Relations with the European Union are reserved or excepted in Scotland and Northern Ireland and are not devolved in Wales. Removing the EU constraints would enlarge devolved competence unless new limits were imposed. Having already held that a United Kingdom statute was required, the majority did not decide whether the Northern Ireland Act 1998 independently required one. Section 75, on equality of opportunity, does not bind a Minister of the Crown, and the withdrawal decision was not a function of the Secretary of State for Northern Ireland carried out in relation to Northern Ireland. Section 1 protects Northern Ireland’s place in the United Kingdom unless a majority in a poll favour a united Ireland. It does not require the consent of the people of Northern Ireland to leaving the European Union, and it creates no legitimate expectation to that effect.
The Sewel Convention is the political expectation that Westminster will not normally legislate on devolved matters without consent. It is recorded in the Memorandum of Understanding and, for Scotland, in section 28(8) of the Scotland Act 1998. The majority held that this statutory recognition recorded a convention; it did not create a rule which courts can interpret or enforce. The Scottish Parliament, the Welsh Assembly and the Northern Ireland Assembly therefore have no legal veto on withdrawal.
The dissent
Lord Reed, with whom Lord Carnwath and Lord Hughes agreed, would have allowed the appeal. He read section 2(1) as conditional on the Treaties applying to the United Kingdom. Once the Lisbon Treaty had been added to the 1972 Act, that condition included article 50, so notice would not alter domestic law by prerogative: the Act would simply cease to import rights. He also treated later express restrictions on other prerogative powers as showing that Parliament limited the prerogative only when it said so. Lord Carnwath considered that notice starts a political process and does not itself remove rights, although legislation would be needed to complete withdrawal. On the distinct Northern Ireland points, the dissentients agreed that sections 1 and 75 did not answer the case and that the Sewel Convention is not legally enforceable.
Verdict: By eight votes to three, the Court dismissed the Secretary of State’s appeal. An Act of Parliament was needed before ministers could give notice. On the devolution issues, the Court unanimously held that consent from the devolved legislatures was not a legal requirement. It did not decide whether an article 50 notice could be withdrawn.
