Supreme Court · 8-3: majority Lord Neuberger, Lady Hale, Lord Mance, Lord Kerr, Lord Clarke, Lord Wilson, Lord Sumption and Lord Hodge; Lord Reed, Lord Carnwath and Lord Hughes dissenting. The devolution points were decided unanimously
Facts
In June 2016 a referendum was held in the United Kingdom, in which a majority voted to leave the European Union. The government proposed to give notice under Article 50 of the Treaty on European Union, starting the process of withdrawal, using the royal prerogative to conduct foreign affairs and make and unmake treaties, without a further Act of Parliament. The claimants argued that only Parliament could authorise such notice.
History
The Divisional Court held for the claimants in November 2016. The government appealed directly to the Supreme Court. A reference on devolution questions from Northern Ireland was heard at the same time, with interventions by the Scottish and Welsh governments.
Issue
Whether the Crown could, in the exercise of the prerogative, give notice under Article 50 without authority from an Act of Parliament; and whether the consent of the devolved legislatures was legally required before Parliament authorised such notice.
Held
Appeal dismissed by 8 to 3. An Act of Parliament was required to authorise ministers to give notice. By a unanimous decision, the legislatures of Scotland, Wales and Northern Ireland had no legal right to be consulted or to consent, since the Sewel convention is not enforceable by the courts.
Ratio
- The prerogative cannot be used to change domestic law or remove rights conferred by statute, and giving notice under Article 50 would inevitably remove rights that derive from the European Communities Act 1972, so ministers could not give notice without statutory authority.
- The Sewel convention, and the rules requiring consultation of the devolved institutions, are political conventions which the courts cannot enforce, so there was no legal requirement for the consent of the devolved legislatures.
The judgments
Lord Neuberger, Lady Hale, Lord Mance, Lord Kerr, Lord Clarke, Lord Wilson, Lord Sumption and Lord Hodge (majority)
In a joint judgment, held that the Crown cannot use the prerogative to alter the law of the land, that the 1972 Act made EU law a source of domestic law and rights, and that withdrawal would change that law so as to require primary legislation. Held that the referendum had political but not legal effect, and that the devolution conventions are not legally enforceable.
Lord Reed (dissenting)
Held that the 1972 Act gave effect to EU law only for so long as the United Kingdom was a party to the treaties, so withdrawal by the Crown did not itself alter domestic law and was within the prerogative.
Lord Carnwath (dissenting)
Dissented on the main question, taking the view that the 1972 Act left the decision whether to remain a member to the treaty-making power of the Crown.
Lord Hughes (dissenting)
Agreed with the dissenting reasoning of Lord Reed that the 1972 Act did not preclude withdrawal under the prerogative.
Key reasoning
- The prerogative permits ministers to make and unmake treaties, but since the Case of Proclamations (1610) and the Bill of Rights 1689 it cannot be used to change the law of the land without Parliament.
- By the 1972 Act, Parliament created a new source of domestic law in EU law, so a decision to withdraw from the treaties would change the law and remove rights of individuals, which the Crown cannot do under the prerogative.
- Nothing in the statutes enacted since 1972, including the European Union Referendum Act 2015, authorised withdrawal without a further Act, since that Act said nothing about the legal effect of the result and was advisory.
- The Sewel convention is recognised in the Scotland Act 1998 but is a political convention, and the courts are concerned with legal rules and not with the operation of political conventions.
Obiter
- The majority observed that the prerogative power to conduct foreign relations remains in place and that the requirement of statutory authority arises only because withdrawal would affect domestic law.
Where it fits in the module
The topic on referendums, recall and direct democracy considers the status of direct democracy in a system based on parliamentary sovereignty. Miller shows that even a major referendum result does not have legal effect without Parliament, and that its political force does not displace the constitutional position of Parliament. The case also addresses the relation between the prerogative and statute and the role of conventions, themes found across the constitutional law course.
Criticisms
- The majority treated the rights derived from the 1972 Act as domestic rights that ministers could not remove, but those rights exist only as long as the treaties, so the reasoning arguably confuses a change of circumstances with a change of law, as Lord Reed argued.
- Holding that the referendum had no legal effect rests on its advisory character, but the decision did not engage with the political force of the result in a system where a statute had put the question to the people.
- The court refused to enforce the Sewel convention, which leaves the position of the devolved institutions, and the effect of s 28(8) of the Scotland Act 1998, dependent on political goodwill.
- The court gave a wide meaning to the principle that the prerogative cannot change domestic law, which risks limiting the power of the Crown over treaties in contexts where domestic effect is indirect.
Written with AI (claude-sonnet-5.5 (Claude Code writer)) on 1 November 2026, reviewed for errors by a second model (claude-sonnet-5.5 (Claude Code checker)). Read the case itself on Find Case Law. Spotted an error? Tell us.