UK Supreme Court hears Indyref2 arguments
Test case on whether Holyrood has power to approve another vote
A case starts today at the UK Supreme Court which could decide whether the Scottish Parliament has the power to legislate for a second referendum on independence.
A panel of five justices will start hearing evidence from the Scottish Government today with the UK Government expected to respond on Wednesday.
The case concerns proposed legislation at the Scottish Parliament called the Scottish Independence Referendum Bill.
Judges have been asked to decide whether the proposed Scottish Independence Referendum Bill relates to "reserved matters" - meaning it is outwith Holyrood's competence.
Nicola Sturgeon asked the Lord Advocate, Scotland's chief law officer, to refer the Bill to the Supreme Court when she published the legistation in June saying she wanted an "indisputably lawful" referendum to take place.
The UK Government, represented in the court by the Advocate General, is opposed to a second referendum.
Here are some of the most important issues:
What will the judges make a ruling on?
At the heart of the case is proposed legislation in the Scottish Parliament called the Scottish Independence Referendum Bill.
This would allow for a second vote on Scottish independence to take place next year.
However, there are questions over the legality of an independence referendum which does not have a section 30 order from Westminster - the legal instrument which can grant Holyrood the power to organise a vote.
The five judges have been asked to decide whether the Bill relates to "reserved matters" - meaning it is outwith Holyrood's competence.
How did this come to court?
When she published the Bill in June this year, Nicola Sturgeon said her opponents would cast doubts on its legitimacy.
The First Minister said she wanted an "indisputably lawful" referendum to take place and sought to head off any legal challenge by referring it to the Supreme Court herself.
This is why the case will be called a "reference" in the Supreme Court.
Who will represent the two sides?
The Lord Advocate Dorothy Bain KC is the Scottish Government's top law officer and is listed as the applicant in the case.
The Advocate General for Scotland, Lord Keith Stewart KC, is listed as the respondent. He represents UK ministers on issues of Scottish law.
His legal team includes Sir James Eadie KC.
What will the UK Government argue?
Both sides have published some of their legal arguments in the months ahead of Tuesday's hearing.
The UK Government, under successive Prime Ministers, has always maintained opposition to a second independence referendum.
In August, the Advocate General asked the Supreme Court to "decline to determine the reference", saying it is outwith the court's jurisdiction.
However, he also argued that even if the court does decide it has jurisdiction over the matter, Holyrood would be unable to hold a lawful referendum.
A referendum plainly relates to reserved matters and is outside Holyrood's legislative competence, he argued.
The Scotland Act states that "the Union of the Kingdoms of Scotland and England" is a reserved matter.
What will the Scottish Government argue?
The Scottish Government's case has leaned heavily on the vote being "advisory" rather than "self-executing" and therefore has no real effect on the Union.
In a 51-page filing submitted in July, the Lord Advocate argued the Bill would simply be to "ascertain the wishes of the people of Scotland on their future".
She wrote: "The legal effects of the Bill would be limited to facilitating the holding of a referendum vote, identifying those eligible to vote, the timing of the vote and affirming that the Referendums (Scotland) Act 2020 would apply."
Who else is involved in the case?
The SNP has submitted its own legal argument to the Supreme Court, separate from the Scottish Government's.
The party was granted the chance to intervene in the case via a written submission.
This document stressed the right to self determination, stating that it must inform the interpretation of the Scotland Act 1998.
What if the Supreme Court rules against the Scottish Government?
Ms Sturgeon accepts that her legal case in the Supreme Court may not be successful.
If this is the case, she says it will not be the court's fault but rather that of Westminster legislation.
In this scenario, she says the SNP will fight the next general election on one issue: "Should Scotland be an independent country?"
The First Minister says this will make the next general election a "de facto referendum".
When might there be a vote?
If the Scottish Government is successful, Ms Sturgeon is proposing to hold the referendum on October 19, 2023.
This is within the SNP's timescale of holding the vote in the first half of the current session of the Scottish Parliament.
When will the Supreme Court decide?
The five judges listed are Lord Reed, Lord Lloyd-Jones, Lord Sales, Lord Stephens and Lady Rose.
While there is no set time for the judgment to be issued, it could be weeks or months away.
Lord Hope, a former deputy president of the Supreme Court, has suggested such a decision could take six to eight weeks.