Since the decision of the High Court that the Government cannot invoke Article 50 using Royal Prerogative, increasing attention has turned to the Supreme Court and the decision they will make on the subsequent appeal, to be heard next week.

The judicial review has got ever more complicated, with increasing numbers of parties involved, and as such, more legal arguments included. The case now features 1 appellant, 2 applicants, 5 respondents, 5 interveners, 2 interested parties and 1 notice party.

So what does the decision next week mean for Theresa May and her self-imposed deadline of triggering Article 50 by the end of March next year?

The easiest scenario for the Prime Minister is that the Supreme Court overturns the High Court’s decision, and she can continue with her plan of invoking Article 50 when she chooses through the Royal Prerogative. Personally, I find this hard to see happening. The High Court’s ruling was made unanimously, is well reasoned and is legally strong. The judges essentially rejected the Government’s argument before even turning to the appellants: the Government therefore has a big task ahead of it to convince the Supreme Court to reverse the decision.

However, of the 92 appeals heard by the Supreme Court between 1 April 2015 and 31 March 2016, it allowed 34 and dismissed 31, with 2 being referred to the European Court of Justice (ECJ), and 5 ending in another result. The Court therefore overturned 49% of the cases it decided on, and as such, its decision in this case is by no means a foregone conclusion.

If the Supreme Court does not overturn the High Court’s decision, then we are likely to see at the very least a ruling that the Government must pass an Act of Parliament to allow it to trigger Article 50. The Government is even preparing such a Bill, so that in the event the Supreme Court does not find in its favour, the Bill can be introduced into the Commons speedily. It is unlikely that MPs would vote against the Bill: they need to think about the electorate, the majority of whom voted to leave the EU, producing a mandate that MPs cannot ignore. Indeed, the Labour Party have already said that they will not seek to block Brexit, so what is more likely is that MPs try to add amendments to the Bill in order to secure more scrutiny of the Brexit process. Their ability to do this will depend on the drafting of the Bill.

Amended or not, the Bill will pass through the Commons. But Theresa May undoubtedly comes up against a bigger problem when the Bill reaches the Lords. Peers don’t have the same need to take voters’ wishes into account, and the majority seem to be on the Remain side. In particular, while the Lib Dems, and their positioning that they will vote against Article 50 unless there is the guarantee of a second referendum on the final deal, does not cause a problem in the Commons – with only 8 (oh wait, 9!) MPs there isn’t much they can do – their numbers are significantly swelled in the Lords. Factor in Baroness Wheatcroft and her plan for a group of cross-party Peers to stall the Bill as much as possible, and there could be a problem.

Luckily for Theresa May, she can turn to the Parliament Acts 1911 and 1949. These Acts together limit the powers of the House of Lords in relation to primary legislation, preventing Peers from having an absolute veto. However, if the Prime Minister does have to use this as a nuclear option to force the Bill through the Lords, she will be significantly delayed in triggering Article 50, as the rules still allow Peers to delay a Bill for one year over two parliamentary sessions.

So, the best-case scenario for Theresa May is that a short Bill passes through both Houses, and with the Government controlling timetabling for this, she is still on track to meet her March deadline. The worst-case scenario is that she is forced to turn to the Parliament Act, with a Bill allowing her to trigger Article 50 only receiving Royal Assent in February 2018 at the earliest.

What if the Supreme Court goes further and rules that a “more comprehensive replacement” of the European Communities Act is required before the Prime Minister can trigger Article 50? The Government is not believed to have started drafting the Great Repeal Bill, and despite its claim that it can easily transpose all EU law into UK statute books, this is going to need to be an incredibly extensive and complex piece of legislation that will take time to draft to ensure that the interlocking nature of EU law is adequately reflected and that the rights provided for work and can be enforced. Despite comments from Lady Hale that this is something the Justices may need to consider, it seems unlikely that a majority would reach this conclusion. However, if they did, it would be a very difficult result for Theresa May.

The Supreme Court judgment could get yet more complicated still. The High Court proceeded on the assumption that Article 50 is irrevocable, and from this, concluded that it is the actual invoking of Article 50 itself that leads to the loss of fundamental rights enshrined in the European Communities Act 1972 (ECA) that will inevitably occur when the UK eventually leaves the EU. The Government conceded this point, presumably for political reasons: they need to stick to their ‘Brexit means Brexit’ rhetoric, and want to avoid a reference to the ECJ, to dodge the outrage among Brexiteers that will inevitably ensue and the delay this would cause.  And it suited the claimants to agree: it made their argument stronger and the Government’s argument weaker. The Government has not changed tact on this, but rather has chosen to ask the Supreme Court to proceed on the same basis, as have the majority of other parties to the case.

However, the making of a preliminary reference to the ECJ under Article 267 of the Treaty on the Functioning of the European Union (TFEU) is not up to the parties; it is up to the Court. If the Court concludes that it is unsure of the correct interpretation of Article 50, and decides that it needs an answer on this point in order to make its judgment, then it must refer to the ECJ.  In this event, the Supreme Court hearing will be suspended until a ruling on the correct interpretation of Article 50 is handed down by the ECJ. The Supreme Court will then resume its proceedings and hand down its own judgment on the case as a whole. So the key question here is: how long will all this take?

The Court of Justice of the European Union (of which the ECJ is part) recently published updated guidance on preliminary references. This states that while a national court can make a reference as soon as it knows it needs to, it is advised to gather all necessary information first, and in the interests of justice, hear both sides of the argument. So we are likely to know that the Court has decided to make a preliminary reference at the earliest on the 8th December, when the hearing concludes, but more likely some time after this, after the Justices have taken the time to discuss whether they believe this is necessary.

The point of law must then be decided by the ECJ, which would involve a hearing in the European court’s 28-member chamber of judges. While cases take on average 16 months to be decided, it is believed this case would meet the requirements for an expedited procedure, essentially fast-tracking the case through the court. However the phrase ‘fast-tracking’ might be misleading: Advocate General Eleanor Sharpston QC, the most senior British member of the ECJ, has recently commented that it is still likely to take 4-8 months.

Following this, the Supreme Court would then proceed with making their judgment on the basis of the interpretation from the ECJ. Worst case scenario for Theresa May under this eventuality is a wait of around 10 months before she even knows if she can proceed using Royal Prerogative or needs to pass a Bill first. That, again, takes us well past the March deadline.

Finally, what about the devolved nations, who have all, one way or another, become involved in the case? The Lord Advocate for Scotland, Counsel General for Wales and the Northern Irish applicants all suggest that the requirement in Article 50 for a member state to follow its “own constitutional requirements” includes constitutional norms, such as those set out in constitutional conventions including the Sewel Convention. This would mean that the (unwritten) UK constitution now expects MPs to canvass the views of devolved legislatures before legislating on devolved matters.

The Government has now published its counterarguments to the devolved administrations’ submissions. As many in the legal sphere have noted, the Government’s legal answers are “unnecessarily rude” and “tetchy”. In a nutshell, they argue the Court is being invited to “stray into areas of political judgment rather than legal adjudication” on the basis that the Sewel Convention is just a political convention and not part of UK constitutional law.

So the decision on whether the devolved nations will have the opportunity to influence the process seems to hang on whether the Sewel Convention is a constitutional or a political notion. Scotland is surely in the strongest position, as the new Scotland Act passed in 2016 went further in inscribing the Convention into the devolved settlement. However, it retained the provision that the UK Parliament “will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament”. Therefore, the Supreme Court’s understanding of the word ‘normally’ could swing their decision on this point, and possibly lead to a ruling that Holyrood’s consent is needed. Neither Scotland nor Wales are arguing for an actual veto on the invoking of Article 50, and as such, even if they win in the Supreme Court, the May Government could still impose Brexit on the devolved nations.

The result is that the triggering of Article 50 is unlikely to be delayed because one of the devolved nations is blocking it. However, this result is one thing legally and entirely another politically. The Scottish Government in particular will not be happy to find out that the UK Government essentially views power devolved as ultimately power retained. Will Scotland use the threat of IndyRef2 to force the Government to accept its conditions on Brexit until it grants its consent?

Overall, while the Supreme Court are ruling on a matter of law, rather than passing political comment, their decisions could have a significant impact on Theresa May’s Brexit timeline. And that’s before even considering the raft of additional legal cases that could be brought further down the line as a result of the legal complications to the Brexit process.

If you thought Brexit was complicated already…

My Trusty Gavel” by Brian Turner is licensed under CC BY 2.0.