Constitutional practice and principle in the Article 50 litigation

The European Union (Notification of Withdrawal) Act 2017 authorised the Prime Minister to give notice under Article 50 of the Lisbon Treaty of the UK’s intention to withdraw from the EU. The Act was adopted in response to R (Miller and Dos Santos) v Secretary of State for Exiting the European Union [2017] UKSC 5, in which the Supreme Court held, by majority, that the royal prerogative did not authorise the Government to begin the process of withdrawal from the EU Treaties. The House of Commons resisted attempts by the House of Lords to include conditions concerning the status of EU nationals and requiring subsequent parliamentary approval. Parliament’s refusal to limit the Government’s power to begin withdrawal from the EU was foreseeable – indeed it was foreseen by Lord Carnwath in his dissent in Miller (at [273]) – in light of the resolution of the House of Commons on 7 December 2016, the third day of the Supreme Court hearing, confirming the House’s support for the Government to trigger Article 50 by 31 March 2017. Not that the litigation was futile. The Supreme Court’s judgment raised the political cost of triggering Article 50, empowering the House of Lords and providing an occasion to oppose withdrawal and/or to propose conditions on notification or withdrawal. It is arguable that the Government ought in any case – quite apart from the law – to have invited the Houses of Parliament to signify their support for triggering Article 50, whether by way of resolutions in each House or by primary legislation. The Constitution Committee of the House of Lords argued as much in its report The Invoking of Article 50 (HL Paper 44, 13 September 2016) and there is much to be said for it.