R (Miller) v Secretary of State for Exiting the European Union [2017]

[2017] UKSC 5, [2018] AC 61 · Supreme Court of the United Kingdom · United Kingdom

Legal Historylegal-historyconstitutional-lawprerogative-powersparliamentary-sovereigntyLegal History

Issue

Whether the Government, acting under the royal prerogative, has the power to give notice under Article 50(2) TEU to withdraw the United Kingdom from the European Union without the prior authority of an Act of Parliament.

Held

The Government cannot use prerogative powers to trigger Article 50 because it would inevitably change domestic law and remove existing statutory rights, which is a matter for Parliament, not the executive, under the constitutional principle of parliamentary sovereignty.

Exam use

In exam answers, use Miller to illustrate: (1) the justiciable limits of the prerogative; (2) that parliamentary sovereignty trumps executive discretion when domestic rights are at stake; (3) the difference between legal and political conventions (Sewel). Distinguish it from cases where the prerogative was allowed (e.g., treaty making without statutory effect). Watch for problem questions asking whether the Government can commit troops to war without a vote - note that Miller does not directly answer that, but the reasoning may be extended.

Summary

The UK Supreme Court held that the Government cannot use prerogative powers to trigger Article 50 TEU and commence withdrawal from the European Union without prior authorisation from Parliament, because such action would alter domestic legal rights and frustrate the constitutional principle of parliamentary sovereignty.

Facts

Following the 2016 referendum on EU membership, the UK Government sought to give notice under Article 50(2) TEU of the UK's intention to withdraw from the European Union. The Government claimed it could use the royal prerogative in foreign affairs to do so without a vote in Parliament. The claimants argued that because the European Communities Act 1972 gave domestic legal effect to EU law, and withdrawal would remove those rights, parliamentary approval was required. The Government contended that the prerogative was broad enough to cover treaty-making and termination. The case was heard by a constitutionally expanded panel of 11 justices. The devolved administrations also sought a role, arguing that the Sewel convention required their consent.

Procedural History

The case was heard in the High Court, which ruled against the Government ([2016] EWHC 2768 (Admin)). The Government appealed directly to the UK Supreme Court. The Supreme Court granted a leapfrog appeal and also heard a related reference from the Northern Irish courts. Judgment was delivered on 24 January 2017 by an 8-3 majority.

Issue

Whether the Government, acting under the royal prerogative, has the power to give notice under Article 50(2) TEU to withdraw the United Kingdom from the European Union without the prior authority of an Act of Parliament.

Held

The Government cannot use prerogative powers to trigger Article 50 because it would inevitably change domestic law and remove existing statutory rights, which is a matter for Parliament, not the executive, under the constitutional principle of parliamentary sovereignty.

Ratio Decidendi

The royal prerogative cannot be exercised by the executive to alter domestic law or to frustrate the will of Parliament as expressed in statute. Because the European Communities Act 1972 is a source of domestic law rights, and withdrawal from the EU would directly contradict its provisions, only Parliament can authorise the steps that lead to the repeal or modification of that Act. The prerogative does not extend to overriding or nullifying statute.

Obiter Dicta

The majority noted that the Sewel convention (that Westminster would not normally legislate on devolved matters without consent) was a political convention, not a legal rule, and was not enforceable by the courts.

Reasoning

The Supreme Court applied the principle from Case of Proclamations (1611) and De Keyser's Royal Hotel (1920) that the prerogative cannot be used to alter the common law or statute. The court distinguished between the treaty-making power (executive) and the domestic legal effect of treaties (legislative). Because the European Communities Act 1972 gave direct effect to EU law, triggering Article 50 would inevitably change domestic legal rights, such as the right of free movement for UK citizens. Therefore, parliamentary authorisation was constitutionally necessary. The court rejected the argument that the 2016 referendum itself provided democratic authorisation, as referendums in the UK are advisory under the Political Parties, Elections and Referendums Act 2000 unless Parliament specifies otherwise.

Plain-English Explanation

Think of the UK constitution as a house: Parliament builds the rooms (statutes), and the Government can only redecorate the existing rooms using the ‘prerogative toolkit’. But the Government cannot demolish a wall that Parliament built (the European Communities Act 1972) just by using the toolkit. Only Parliament can authorise demolition. In Miller, the Supreme Court said the Brexit notification would start demolishing the wall, so the Government had to ask Parliament first. This protects the fundamental principle that the people's elected representatives, not the Government alone, control the laws that govern our rights.

Essay-Ready Explanation Generator

Version 1 of 4

Reference to R (Miller) v Secretary of State for Exiting the European Union ([2017] UKSC 5, [2018] AC 61) strengthens a Legal History answer because the case reflects the principle that The royal prerogative cannot be exercised by the executive to alter domestic law or to frustrate the will of Parliament as expressed in statute. Because the European Communities Act 1972 is a source of domestic law rights, and withdrawal from the EU would directly contradict its provisions, only Parliament can authorise the steps that lead to the repeal or modification of that Act. The prerogative does not extend to overriding or nullifying statute. Applied to a problem question, the case should be used after identifying the issue as Whether the Government, acting under the royal prerogative, has the power to give notice under Article 50(2) TEU to withdraw the United Kingdom from the European Union without the prior authority of an Act of Parliament. The stronger essay move is to connect the material facts to the court's holding, then explain whether the present facts support the same conclusion or justify distinguishing the authority.

Underlying Concepts

  • parliamentary sovereignty
  • royal prerogative
  • separation of powers
  • constitutional conventions
  • rule of law

Precedents Applied

  • Case of Proclamations (1611)
  • De Keyser's Royal Hotel (1920)
  • Attorney-General v De Keyser's Royal Hotel Ltd (1920)

Later Treatment

  • R (Miller) v The Prime Minister and Cherry v Advocate General for Scotland (2019) – on prorogation
  • R (on the application of the Good Law Project) v Prime Minister (2021)

Key Passages

  • 'The major change in the constitution of the United Kingdom which would be brought about by withdrawal from the European Union requires parliamentary approval.' – Lord Neuberger, para 82
  • 'The prerogative power to make and unmake treaties is not sufficient to justify the abrogation of particular domestic statutes.' – Lord Carnwath, para 131

Significance

This case is a landmark in UK constitutional law, reaffirming the supremacy of Parliament and the limits of executive power. It demonstrates that even in areas traditionally governed by the prerogative, such as foreign affairs, the executive cannot act if it would undermine or contradict statute. The case is a key authority for the separation of powers, rule of law, and the constitutional requirement that major changes to the legal order must be approved by the legislature. It is frequently contrasted with the US approach in cases like INS v Chadha, and is essential for understanding the UK's unwritten constitution.

Related Cases

Exam Tips

In exam answers, use Miller to illustrate: (1) the justiciable limits of the prerogative; (2) that parliamentary sovereignty trumps executive discretion when domestic rights are at stake; (3) the difference between legal and political conventions (Sewel). Distinguish it from cases where the prerogative was allowed (e.g., treaty making without statutory effect). Watch for problem questions asking whether the Government can commit troops to war without a vote - note that Miller does not directly answer that, but the reasoning may be extended.

Revision Checklist

  • Name the issue before discussing facts so the marker sees the legal question immediately.
  • State the holding in one sentence, then use the ratio to explain why the court reached that result.
  • Use the citation and jurisdiction to show why this authority matters for the problem you are answering.
  • Pair this case with one supporting or contrasting authority if the question tests limits, policy, or exceptions.

Problem Question Use

If a problem question involves the executive attempting to change domestic law or rights by fiat, cite Miller as authority that only Parliament can authorise such changes. Use it to counter arguments that the executive's foreign affairs powers are unlimited. For example, in a question about a government decision to withdraw from a treaty that gives citizens enforceable rights, Miller requires statutory authorisation. If the question involves a referendum, note that Miller confirmed referendums are advisory unless Parliament states otherwise, so a referendum result alone does not authorise governmental action altering statute.

Common Pitfalls

  • Assuming the case holds that the Government cannot trigger Article 50 at all (it can, but only with a vote)
  • Confusing the Sewel convention ruling with a legal limit on Westminster
  • Overstating the breadth of 'altering domestic law' – only changes that directly contradict statute are caught

Sources