Brexit: UK Supreme Court Holds That An Act Of Parliament Is Necessary To Trigger Brexit Negotiations

The Supreme Court has upheld the High Court's decision in Miller v Secretary of State for Exiting the European Union. Its judgment confirms that an Act of Parliament is required to authorise the Government to begin the process of the UK leaving the EU under Article 50 of the Treaty on European Union. Political indications are that the House of Commons is likely to approve the bill, following their motion on the same topic last year. The position of the House of Lords is less certain. This memorandum analyses the impact of the Supreme Court's decision and discusses the options available to the Government.

The Supreme Court Decision

Article 50 of the Treaty on European Union ("TEU") provides that a member state may withdraw from the EU by notifying the European Council of its intention following a decision made "in accordance with its own constitutional requirements." The UK Government had argued that the European Council could be notified by the Government under the royal prerogative. 1 This argument was rejected by the High Court in Miller v Secretary of State for Exiting the European Union, which held that an Act of Parliament was required. 2 That decision was appealed to the Supreme Court. 3 For the first time ever, all eleven members of the Supreme Court heard the appeal, reflecting the constitutional and political importance of the case.

In upholding the decision of the High Court, and confirming that the Government lacks the legal authority to trigger Article 50 without statutory authority, Lord Neuberger, writing for the majority in an 8-3 split, explains at paragraph 86 of the judgment:

" [T]he EU Treaties not only concern the international relations of the United Kingdom, they are a source of domestic law, and they are a source of domestic legal rights many of which are inextricably linked with domestic law from other sources. Accordingly, 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."

The effect of the judgment renders any Article 50 notification given by the Prime Minister to the European Council without Parliamentary approval legally ineffective as a matter of domestic law and EU law. 4 This is because such notification would also fail to comply with Article 50(1), which requires a Member State to withdraw from the EU "in accordance with its own constitutional requirements." 5

To pass an Act of Parliament, the Government will need to introduce a bill for the approval of both the House of Commons and the House of Lords. The bill becomes an Act of Parliament following the approval of both Houses and Royal Assent. 6

Key: 1 - First Reading 2 - Second Reading C - Committee Stage R - Report Stage 3 - Third Reading A - Consideration of Amendments Figure produced using Parliament's guide to the passage of a Bill (available here).

House of Commons

Prior to the EU referendum on 23 June 2016, 480 out of 650 MPs stated that they intended to vote to remain in the EU. 7 It is anticipated now, however, that the Prime Minister will be able to whip almost all Conservative MPs, save for the few expected hold-outs, to vote in favour of the Government's bill authorising the Government to issue a notification under Article 50. Jeremy Corbyn, the Leader of the Opposition, has previously indicated Labour's willingness to prevent the Prime Minister from triggering Article 50 if she fails to agree with Labour's "Brexit bottom line." 8 This 'bottom line' includes, inter alia, access to the single market. 9 However, it was later clarified that Labour would not block an Act of Parliament but would rather seek to influence and amend the Government's terms of negotiation. 10 Since this clarification, members of Jeremy Corbyn's shadow cabinet have indicated their intention to refuse to vote for a bill to trigger Article 50. 11 This signals the willingness of some MPs to obstruct the passage of the bill through the House of...