R (on the application of Miller and another) v Secretary of State for Exiting the European Union

The prerogative power to make and terminate treaties does not permit ministers, without statutory authority, to alter domestic law, remove statutory rights or extinguish a source of domestic law created by Parliament. Notification of withdrawal from a treaty therefore requires primary legislation where its inevitable effect would be a fundamental change in domestic law.

The legal effect of a referendum depends on its authorising statute. A referendum which carries no prescribed legal consequences has political force but cannot itself change the law. Constitutional conventions, including the Sewel Convention, remain political and non-justiciable even when recognised in legislation.

The Secretary of State appealed against the Divisional Court’s decision in R (Miller) v Secretary of State for Exiting the European Union [2016] EWHC 2768 (Admin). That court held that ministers could not use the Royal prerogative to give notice under article 50 of the Treaty on European Union without prior statutory authority.

The Supreme Court also considered references arising from Northern Irish judicial review proceedings. The Northern Ireland High Court had rejected devolution arguments in Re McCord, Judicial Review [2016] NIQB 85.

The central question was whether ministers could initiate the United Kingdom’s withdrawal from the European Union without primary legislation. Further questions concerned the effect of the referendum, the Northern Ireland devolution settlement and the Sewel Convention.

1. Disposition. By a majority of eight to three, the Supreme Court dismissed the Secretary of State’s appeal. Ministers required authority conferred by primary legislation before giving notice under article 50(2) of the Treaty on European Union.

2. Prerogative and domestic law. Parliamentary sovereignty prevents ministers from using prerogative powers to change statute or common law, remove statutory rights or frustrate legislation. The treaty-making prerogative ordinarily operates only on the international plane because unincorporated treaties neither create nor remove domestic rights. Although prerogative action may alter facts to which existing law applies, that exception did not authorise the constitutional changes resulting from withdrawal.

3. The constitutional effect of the European Communities Act 1972. The Act made EU law an independent and overriding source of domestic law while preserving Parliament’s ultimate sovereignty. Withdrawal would extinguish that source, change the status of EU-derived rules and remove some domestic rights. That change differed in kind from ordinary variations in EU law accommodated by section 2. The Act neither created nor preserved a ministerial power to terminate the statutory system. The majority disapproved R v Secretary of State for Foreign and Commonwealth Affairs, Ex p Rees-Mogg [1994] QB 552 insofar as it indicated otherwise, while accepting that its result was correct because the protocol there considered did not significantly alter domestic law.

4. Referendum. The legal consequences of a referendum depend on the statute authorising it. The European Union Referendum Act 2015 required a referendum but prescribed no legal consequence. The result therefore had great political force but did not authorise ministers to alter domestic law. A House of Commons resolution was likewise not legislation.

5. Devolution. The devolution statutes assumed EU membership but did not require it to continue. EU relations were not devolved. Section 1 of the Northern Ireland Act 1998 concerned whether Northern Ireland remained within the United Kingdom, not EU membership. Section 75 did not constrain the proposed notification. The Sewel Convention remained a political convention, notwithstanding its statutory recognition, and the devolved legislatures had no legally enforceable veto over withdrawal legislation.

6. Dissent. Lord Reed, with whom Lord Carnwath and Lord Hughes agreed on the main issue, considered section 2(1) of the European Communities Act 1972 inherently conditional on the Treaties continuing to apply. On that construction, withdrawal would cause the statutory scheme to cease operating without changing the Act, so ministers could give notice under the treaty prerogative.

1. United Kingdom Supreme Court: In R (on the application of Miller and another) v Secretary of State for Exiting the European Union [2017] UKSC 5, the court dismissed the Secretary of State’s appeal by eight to three. It also determined or treated as superseded the referred Northern Ireland questions.
2. Divisional Court of England and Wales: In R (Miller) v Secretary of State for Exiting the European Union [2016] EWHC 2768 (Admin), the court held that ministers could not give article 50 notice without statutory authorisation.
3. High Court of Northern Ireland: In Re McCord, Judicial Review [2016] NIQB 85, Maguire J rejected the Northern Ireland constitutional and devolution arguments. Questions from related proceedings were referred to the Supreme Court, and the Northern Ireland Court of Appeal referred a further issue.