## Facts

- A 2016 UK referendum produced a majority vote to leave the European Union.
- The Government announced it would notify the European Council under Article 50 of the Treaty on European Union to begin the withdrawal process.
- Claimants sought judicial review, arguing ministers could not trigger Article 50 using prerogative foreign-affairs powers without an Act of Parliament.
- The Divisional Court held that statutory authorization was required because Article 50 notification would affect domestic law and rights created by Parliament.
- Related Northern Ireland proceedings and devolution-related references were heard together with the Government’s appeal to the Supreme Court.

## Issues

1. Whether ministers may use prerogative powers in foreign affairs to give Article 50 notice without prior authorization by an Act of Parliament.
2. Whether Article 50 notification would, as a matter of domestic law, alter or remove statutory rights arising under the European Communities Act 1972 and related legislation, thereby limiting prerogative power.
3. Whether devolution legislation and the Sewel Convention legally require consent of devolved legislatures before Article 50 notice can be given.

## Decision

- The Supreme Court dismissed the Government’s appeal by an 8–3 majority.
- The Court held ministers could not lawfully give Article 50 notice using prerogative powers alone; an Act of Parliament was required.
- The Court held unanimously that devolution statutes and the Sewel Convention did not impose a legal requirement to obtain devolved legislative consent before Article 50 notification.

## Legal Principles

- Prerogative powers cannot be used to change domestic law or to remove statutory rights unless Parliament has authorized that result.
- Under a dualist system, treaties operate in international law; domestic legal effects depend on incorporation by statute.
- The European Communities Act 1972 established EU law as a direct source of domestic law and conferred statutory rights and remedies; executive action that would frustrate that statutory scheme requires parliamentary authorization.
- Article 50 notification was treated as initiating a process that would lead to withdrawal and the loss of statutory EU-derived rights; initiating that process therefore required legislation.
- A referendum may be politically significant but has no legal effect on domestic law unless Parliament clearly provides otherwise.
- The Sewel Convention is a political convention and not legally enforceable by courts; it does not create a legal veto for devolved legislatures over UK-wide legislation or treaty-withdrawal steps reserved to the UK.

## Conclusion

The Supreme Court held that only Parliament may authorize Article 50 notice because it would lead to the removal of statutory rights created through primary legislation, while rejecting arguments that devolution arrangements or the Sewel Convention imposed a legally enforceable requirement of devolved consent.


R (Miller) v. Sec’y of State for Exiting the Eur. Union, [2017] UKSC 5 (UK 2017)