First Minister Nicola Sturgeon announced this week that the Scottish Government is aiming to hold a second Scottish independence referendum on 19 October 2023, and to that end it has published a Scottish Independence Referendum Bill. However, that Bill has not yet been introduced into the Scottish Parliament and, as a preliminary matter, the Lord Advocate is referring to the UK Supreme Court the question of "whether the provisions in [the] Bill relate to reserved matters".

What's the issue?

Essentially, the question is: does the Scottish Parliament have the power to legislate for an independence referendum without the consent of the UK Parliament? This is exactly the same question with which I opened a piece I wrote for The Journal almost ten years ago, demonstrating that it is no closer to being answered now than it was then (even if many of the other issues covered in that piece now look quite different).

Section 29(1) of the Scotland Act 1998 provides that an Act of the Scottish Parliament is not law so far as any provision of the Act is outside the legislative competence of the Parliament, including if it "relates to reserved matters" (section 29(2)(b)). Reserved matters are set out in Schedule 5 to the Act, the first paragraph of which covers various aspects of the constitution including "the Union of the Kingdoms of Scotland and England". Section 29(3) of the Scotland Act provides that the question of whether legislation relates to a reserved matter is to be determined by reference to the purpose of the legislation, having regard (among other things) to its effect in all the circumstances.

The Scottish Government takes the view that the Bill would not relate to the reserved matter of the Union because the referendum would only be consultative rather than self-executing (i.e. a vote in favour of independence would not itself end the Union). Others, and most importantly the UK Government, take the view that a referendum on Scottish independence cannot be said to relate to anything other than the Union. The only way to resolve the argument authoritatively is by the courts deciding whether and how that reserved matter would apply to legislation such as the Bill. To date, no court has pronounced on the issue.

How did the last referendum happen then?

The Scottish Parliament's legislative competence can be amended by way of an Order in Council made by the UK Government under section 30 of the Scotland Act (i.e. a "section 30 Order"). That route was used in relation to the 2014 referendum (pursuant to the so-called "Edinburgh Agreement"), following which the Scottish Parliament passed legislation that – thanks to that order – was undoubtedly lawful: see my 2012 Journal piece for more on that.

While the First Minister said in her statement that she is seeking a new section 30 Order, the UK Government is on record that it has no intention of granting one. The question of whether the Bill would be within the Scottish Parliament's legislative competence will therefore not be resolved that way.

So what's happening with the Supreme Court?

The Lord Advocate is using her power under paragraph 34 of Schedule 6 to the Scotland Act to "refer to the Supreme Court any devolution issue which is not the subject of proceedings" – i.e. not already before a court. The concept of "devolution issue" covers a wide range of questions relating to devolution.

Notice of the reference has been served on the Advocate General for Scotland, the UK Government's Scottish Law Officer, who can be expected to engage with the proceedings to argue that the Bill would relate to the reserved matter of the Union.

How long might the process take?

We are in largely uncharted territory in terms of the procedure to be followed, as this is the first time a reference has been made under paragraph 34 (although the Attorney General for Northern Ireland has previously made two references to the Supreme Court under the equivalent provision for Northern Ireland). The Court has issued a short statement confirming receipt of the reference and noting the first step in the process, which is for the President of the Supreme Court Lord Reed (who is one of the two Scottish Justices) to consider the reference and decide how it should be dealt with.

That statement notes that the Court cannot yet confirm when the case will be heard, though we can make an educated guess. While the Court can be expected to give the reference some priority over its usual caseload, it seems unlikely that it could be heard before the end of the current court term at the end of July. That would mean October at the earliest for a hearing. While a judgment would no doubt also be prioritised, it could well be into December or even Q1 of 2023 before there is a decision.

What are the potential outcomes?

There are three main potential outcomes.

The first is that the Supreme Court considers the question referred and decides that the Bill would not relate to reserved matters. That would (absent some intervening UK Parliament legislation) no doubt be viewed as clearing the way for the Scottish Parliament to pass the Bill for the proposed referendum in October 2023.

The second is that it considers the question referred and decides that the Bill would relate to reserved matters. That would mean the Bill could never be valid law (and indeed the Ministerial Code would preclude a Scottish Minister from even introducing the Bill to the Parliament, as the Law Officers must first sign off on a statement that any given Bill is within competence). In this scenario, the First Minister said the Scottish Government would not pursue the Bill. Instead, the SNP would treat the next UK general election as a de facto referendum on independence, with candidates essentially standing on a single-issue platform.

The third option is that the Supreme Court declines to consider the reference, which is how it dealt with the two Northern Irish references mentioned above: see here and here. In that scenario, the Court would express no view on the reserved matters question (and may not even hear arguments on the point). While the First Minister noted in her statement that it was for the Court to decide whether to accept the reference, she did not cover what would happen in that event: it may be that this would also result in a reversion to the 'general election strategy'.

This latest chapter in the Scottish independence debate is only just beginning.