This post has been contributed by Mrs Hilaire Barnett, Module Content Developer for Public law.
It is six months since the British people voted in a referendum to leave the European Union (EU). The consequences of leaving — economic, legal and political — were unclear at the time of the referendum and have not become any clearer since. From the perspective of constitutional law one key question involves the correct legal base from which to start the process of withdrawing from the EU.
Article 50 of the Treaty of European Union provides that a Member State ‘may decide to withdraw from the Union in accordance with its own constitutional requirements’. Once notification to withdraw has been given, a two year period follows during which the terms of withdrawal and future relations with the EU are negotiated. It is the meaning of the phrase ‘in accordance with its own constitutional requirements’ that has given rise to arguments over whether Article 50 can be triggered under the royal prerogative or whether only Parliament can authorise the notification to withdraw.
For an in depth discussion of the issues see the House of Lords Select Committee on the Constitution, Fourth Report Session 2016 – 17, HL Paper 44.
The arguments are being tested before the courts, and two cases — one in the High Court of Northern Ireland, one heard in the High Court in England — have been decided differently. In McCord, Re Judicial Review; Agnew and Others v Same  NIQB 85 the applicants’ principal ground for judicial review was that the prerogative power had been displaced by the Northern Ireland Act 1998 (and other devolution provisions) and that an Act of Parliament was required to trigger Article 50. The High Court ruled, however, that there were no statutory provisions which expressly (or by necessary implication) limited or altered the Crown’s prerogative power in relation to notification under Article 50. Mr Justice Maguire for the Court ruled that (contrary to the position taken by the High Court in London in the Millar case discussed below) giving notification under Article 50 did not initiate an irreversible process and as such did not alter the law of the United Kingdom or the rights of individual citizens.
In R (Gina Millar and Others) v Secretary of State for Exiting the European Union  EWHC 27768 (Admin) the High Court also considered the question whether the government (in the name of the Crown) could use prerogative powers to give notice under Article 50. The principal argument for the claimants was that the Crown’s prerogative powers cannot be used by the government to ‘diminish or abrogate rights under the law of the United Kingdom’ unless Parliament has given authority to the Crown to do so. Both parties accepted that triggering the Article 50 process was irreversible and would inevitably lead to the UK leaving the EU at the end of the two year period. There is no formal mechanism for halting or withdrawing from the Article 50 process. However it has been argued that the process is not irreversible: see House of Lords European Union Committee, Eleventh Report of 2015 – 16, HL 138. Accordingly, it follows that the rights conferred under EU law will inevitably be diminished or repealed and that the giving of notice under Article 50 would remove the real decision over rights from Parliament. For the government it was argued that Parliament could choose to leave prerogative power in the hands of the Crown, even if its use would result in a change to common law and statutory rights. To remove the prerogative required express words in a statute (or words which led to a necessary implication that this was intended) and no such words could be found in the ECA 1972 or any other statute.
Central to the High Court’s reasoning was the interpretation of the European Communities Act 1972. The Court emphasised that statutory interpretation must be undertaken in light of the various presumptions which underpin legislation. Of particular importance here was the principle that — unless Parliament legislates to the contrary — the Crown ‘should not have power to vary the law of the land by the exercise of its prerogative powers’. The Court recognised that the ECA 1972 was a statute of ‘special constitutional significance’ and ‘the wide and profound extent of the legal changes in domestic law created by the ECA 1972′ . That, the Court ruled, made it especially unlikely that Parliament intended to leave their continued existence in the hands of the Crown’. Moreover, Parliament having legislated to accept the direct effect of EU law, it was ‘… not plausible to suppose that it intended that the Crown should be able by its own unilateral action under its prerogative powers to switch it off again’ (see paragraph 87).
Accordingly, having interpreted the ECA in light of the constitutional background and principles, the Court concluded that …. ‘the Crown … has no prerogative power to effect a withdrawal from the relevant Treaties by giving notice under Article 50 of the TEU’ (at paragraph 92). Appeal to both cases were considered by the Supreme Court in December 2016 and judgment is expected in January 2017.
Proceedings before the Supreme Court may be viewed here.