R (on the application of Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5

Key point

  • Government lacks the authority, through use of prerogative powers, to bring about the removal of EU law as an independent source fundamental constitutional change
  • EU law, by virtue of section 2 of the European Communities Act 1972, had become a source of domestic law, to give notice under Article 50 would entirely remove this source of domestic law,  a significant constitutional change that requires the consent of Parliament


  • Under the dualist legal system in the UK, the authority to enter and break treaties is a prerogative power exercised by ministers on behalf of the Crown and treaties only have effect in international law – to have effect in domestic law they must be implemented by an Act of Parliament
  • The EU Treaties including the TEU, however, are exceptions as they took effect in domestic law through the European Communities Act 1972, through s.2, which incorporated EU law and rulings from the European Court of Justice, into domestic law


  • In 2017, following the 2016 Brexit referendum, the UK Government announced its intention to trigger Article 50 of the Treaty on European Union (TEU) to withdraw from the EU
  • Miller and others sought in the High Court to bring an action for judicial review, claiming that the Government did not have the right to give the notice under article 50 without a vote in Parliament permitting it.
  • The High Court considered that the Government did not have the authority to issue the notice under article 50, but allowed appeal to the Supreme Court.
  • This was the first case to ever be heard en banc by the Supreme Court – i.e. with the full contingent of justices (11 in this case, with one vacancy).

Held (Supreme Court)

Appeal dismissed; the Government could not issue a notice under article 50 without the approval of Parliament.

Lord Neuberger (Majority Judgment)

Nature of the ECA

  • The ECA ‘authorises a dynamic process by which, without further primary legislation…EU law not only becomes a source of UK law, but actually takes precedence over all domestic sources of UK law, including statutes’, but it does not change the ‘fundamental rule of recognition (ie the fundamental rule by reference to which all other rules are validated)’: [60]
  • The ECA is not the source of EU law itself, rather it established various EU institutions as sources of UK law: [61]
  • The ECA merely acts as a ‘conduit pipe’ for EU laws to enter domestic law: [65]

Can the ECA be repealed by Parliament?

  • The ECA is a constitutional statute and thus cannot be implicitly displaced by legislation inconsistent with it: [66]
  • However, Parliamentary Sovereignty still remains in place, thus the ECA can be expressly repealed by Parliament at any time, even if the legislation is inconsistent with EU law: [67]

Removal of EU as a source of law

  • Withdrawal from the Treaties through notice by the executive alone had not been contemplated by s2(1) ECA 1982 as withdrawal is fundamentally different from variations in the content of EU law arising from further EU Treaties or legislation: [78]
  • A complete withdrawal amounts to a ‘fundamental change in the constitutional arrangements’ since it removes EU law, which has become a ‘independent and overriding source of domestic law’ by virtue of the ECA: [78], [80]
  • Withdrawal without parliamentary approval ‘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.’: [81]

Alteration of domestic rights by prerogative

  • EU Treaties not only concern the international relations of the United Kingdom, they are a source of domestic law and domestic legal rights: [86]
  • Under the dualist system in the UK, the Royal prerogative to make and unmake treaties, which operates wholly on the international plane, cannot be exercised in relation to the EU Treaties, at least in the absence of domestic sanction in appropriate statutory form, which the ECA does not provide: [86]

Lord Reed (Dissenting)

Construction of s2(1) ECA

  • Under s2(1) the application of EU law in domestic law is dependent on the contingency of the UK being part of the EU Treaties, and since s2(1) is silent on whether Parliamentary approval is required to withdrawal from the EU Treaties, if prerogative power is exercised to withdraw the UK, no further Parliament approval is required: [197]

Withdrawal will not alter domestic rights

  • Withdrawal would also not alter alter EU rights or the effect given to them in domestic law since it is open to Parliament to enact legislation to protect such rights before withdrawal occurs: [218]
  • Furthermore, since s2 contemplates that withdrawal can be made without parliamentary approval, the alteration of domestic law in the event of withdrawal by notice under Article 50 would be brought about by the ECA rather than prerogative: [219]

Withdrawal does not remove a source of law

  • The rule of recognition is ‘the foundational rule in a legal system which identifies the sources of law in that system and imposes a duty to give effect to laws emanating from those sources’: [223]
  • The UK’s entry to the EU did not change the rule of recognition, citing Lord Mance in Pham: [224]
  • Under the UK’s rule of recognition, the source of law in the UK is Parliament, and the validity of EU law in domestic law depends on an Act of Parliament: [226]
  • Thus EU law is not an independent source of domestic law: [227]


  • On the fundamental level, this was a case of the prerogative power of the Crown being subjugated to the principle of Parliamentary sovereignty
  • This case, and Miller 2 two years later, were both incredibly politically charged and were faced with huge political and pubilc reaction, accusing the judges of judicial activism
  • The opinion of the majority that EU law constituted an independent source of domestic law was consistent with that of the ECJ (see Case 26/62 Van Gend en Loos) while the opinion of Lord Reed that statute was the source of EU law contradicts the position of the ECJ, but is consistent with earlier obiter dicta in UK courts, such as by Lord Mance in Pham