The Supreme Court has this morning (24 January) handed down its judgment in the case of Miller and Dos Santos v Secretary of State for Exiting the European Union and the Northern Irish cases of McCord and Agnew.

In a majority verdict, eight of the 11 judges who sat on the case have upheld the judgment of the Divisional Court that it is for Parliament to make the decision to trigger Article 50 and so to begin the process that will lead the UK out of the EU. The remaining three judges agreed with the government that it could use its prerogative powers to do so.

The judges were unanimous in finding that the government does not have to seek the consent of the devolved legislatures in Scotland, Wales and Northern Ireland to the legislation that will now need to be passed.

In this note we examine the impact of the judgment on the next steps in the Brexit process.

Background and the Court's determination

We have outlined the background to, and issues in, Miller and McCord and Agnew in previous alerts. Both cases concern the central question of whether authorisation from Parliament is required before the government can commence the process for leaving the EU set out in Article 50 of the Treaty on European Union.

The government argued that such authorisation was not required as it could use its power under the royal prerogative to issue the notice required under Article 50. The claimants in Miller and the applicants in McCord and Agnew disagreed and argued that legislation would be required before a notice could be issued.

The Northern Ireland High Court parked that point, focusing instead on whether legislation was also required by virtue of the effect of Brexit on Northern Ireland's constitutional arrangements and whether the Northern Ireland Assembly would need to consent. The Scottish and Welsh governments intervened in the proceedings before the Supreme Court to argue that consent to the required legislation would also be required from the Scottish Parliament and the Welsh Assembly.

With respect to the main point, eight of the 11 Justices (Lord Neuberger, Lady Hale and Lords Mance, Kerr, Clarke, Wilson, Sumption and Hodge) agreed with the Divisional Court in Miller that legislation is needed to authorise the government to trigger Article 50. In a single judgment, the majority held that through the European Communities Act 1972, Parliament has made EU law an independent source of UK domestic law, transferring some of its own law-making powers to the EU institutions, unless and until it decides otherwise.

Triggering Article 50 will have the inevitable effect of the UK leaving the EU thus cutting off that source of law. It will also remove some domestic rights of UK citizens. Both of those consequences require authorisation by an Act of Parliament.

The minority (Lords Reed, Carnwath and Hughes) held that the 1972 Act made the application of EU law in the UK conditional on the UK's membership of the EU and did not impose any requirement in respect of that continued membership. On this view, triggering Article 50, of itself, would not lead to any change in the rights of UK citizens as those rights would be dealt with during the subsequent negotiations. The three dissenting Lords held that the exercise of prerogative powers by the government would not, therefore, frustrate the intention of Parliament nor abrogate domestic rights.

With respect to the role that the devolved legislatures should play in triggering Article 50, the Court was unanimous in its finding that the UK Parliament is not required to seek the consent of the Scottish Parliament or the Northern Ireland and Welsh Assemblies to the legislation required to trigger Article 50.

So what does the Court's determination mean for Brexit?

Brexit will still happen

The Supreme Court's decision will neither legally derail Brexit, nor in practice hold it up. The Prime Minister has committed to triggering Article 50 by the end of March this year and, on 7 December 2016, MPs backed that timetable by a majority of 372. Labour leader, Jeremy Corbyn, has signalled that Labour MPs will be encouraged to support any legislation that is put forward to trigger Article 50. Even accounting for some rebellion in the Labour ranks and opposition from the Liberal Democrats and Scottish National Party, the legislation will pass in the Commons.

The Lords too are unlikely to frustrate the triggering of Article 50 with Lord Fowler - speaker of the House of Lords - commenting that the upper chamber recognises the democratic mandate held by the Commons and will not 'sabotage' the Bill. This is unsurprising as the Lords will be alive to the fact that any attempt by them to thwart the Bill is likely to be met with calls for radical reform of the upper chamber.

The Supreme Court has also effectively ruled out the possibility of the devolved legislatures having any 'veto' over the legislation, or that it could be held up by the impending elections to the Northern Ireland Assembly.

The required legislation is likely to be passed quickly

An Act can be passed in as little as a day with the agreement of Parliament. However, Parliament will want to ensure that it has the opportunity adequately to scrutinise and debate the legislation, and some sources suggest that the government will aim for a two week passage through Parliament.

Following the judgment, David Davis - the Secretary of State for Exiting the EU - confirmed to the House of Commons this afternoon that the government will introduce a Bill within days.

The opportunity to enshrine Parliamentary oversight of the negotiations

MPs will also want to ensure that they have adequate opportunity to amend the Bill and it is the potential for such amendments that is the most interesting outcome of these cases. By ruling that legislation is required to trigger Article 50, the Supreme Court has given Parliament an important lever which it can use to try to shape its role in the subsequent negotiating process.

The Secretary of State for Exiting the EU has confirmed to the House of Commons that Parliament will be kept as well informed during the negotiations as the European Parliament.

Under the 2010 Framework Agreement on relations between the European Parliament and the European Commission, MEPs have the right to be kept informed of developments during treaty negotiations (including access to confidential information), to comment on the developing text and to receive explanations as to how those comments have been taken into account. MPs may well seek to enshrine similar rights in the Bill or to go beyond them.

Parliament's ability to make amendments will depend on the form and wording of the Bill when first introduced. This is because any proposed amendment must be within the reasonable limits of a Bill's collective purposes, as defined by its existing clauses and schedules. The Court declined to comment on what form the required legislation should take, stating that this is 'entirely a matter for Parliament'. The government will therefore wish to introduce a short and tightly drafted Bill which will be hard to amend and there are claims that it has prepared a three line Bill with this in mind.

It is also unlikely that any amendment will be able to result in actions which cost money as the government will not introduce a money resolution which would be required to authorise any such expense.

Why the nature of the oversight is important for businesses

The nature of Parliament's oversight of the negotiating process is important not just from a constitutional perspective, but also because it will shape the opportunities that businesses have to input their views during that process.

It is very unlikely that the Department for Exiting the EU will continue its programme of roundtable discussions with businesses once negotiations are underway. At this point, businesses - primarily through relevant trade associations - will have the opportunity to present their views to the Select Committee on Exiting the EU and other relevant Parliamentary committees. The efficacy of such committees will depend on what information they are provided with as well as whether they are given any formal role in the negotiating process. Trade associations may also be consulted directly by government negotiators keen to understand the consequences of certain positions as the process develops.

However, to the extent that the bulk of MPs are given some role in overseeing the negotiation on the floor of the House of Commons, individual businesses will have the opportunity to lobby their local MP on the issues that are important to them.

Other Brexit issues before the Courts

Finally, it is worth noting that the Miller, Agnew and McCord cases are not the government's only Brexit headache in the courts. We understand that on 3 February the High Court will consider whether or not to grant permission to a judicial review arguing that withdrawal from the EU does not automatically entail withdrawal from the European Economic Area (EEA) and that separate notice is required, together with Parliamentary consent before it can be given. It is hard to see how the EEA Agreement could operate with respect to the UK should withdrawal from the EU not terminate EEA membership - certainly the UK would be stripped of many of the benefits of membership. However, the point may be moot given the Prime Minister's declared aim to leave the Single Market and Labour's broad acceptance of that position.

The EEA question will also be raised in proceedings being contemplated before the High Court in the Republic of Ireland. Those proceedings will also seek a referral to the Court of Justice of the EU to establish whether, once triggered, Article 50 can be revoked. It was the government's position in Miller that Article 50 is not reversible and the Prime Minister has stated her willingness to leave the EU with no deal should what is offered prove unsatisfactory. In her speech on 17 January Mrs May also confirmed that Parliament would be given a vote on any deal before it entered into force. This would go further than Parliament's role with respect to the ratification of treaties under the Constitutional Reform and Governance Act 2010.

Although the government will almost certainly get legislation through Parliament to trigger Article 50, a ruling by Court of Justice of the European Union (CJEU) that the withdrawal process can be reversed has the potential to lead to calls to revoke the Article 50 notice in the face of a bad deal from the EU, rather than simply leaving with no deal and reverting to the World Trade Organisation's (WTO) trading rules. Legally, the question on reversibility is finely balanced; politically it has the potential to change the dynamic of the negotiation and Parliament's willingness to veto any deal.