The government is appealing against the high court ruling, but at the supreme court hearing, the Scottish government will argue that the consent of Holyrood is also required to trigger article 50. Soubry thinks it has a strong case. "Yes. I'm reliably informed that the Scotland Act 2016 section 2 says that you cannot interfere with devolved Scottish matters, they must be determined by the Scottish parliament."
Here is what the Scotland Act actually says:
"... it is recognised that the Parliament of the United Kingdom will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament."
Of course, Scotland is hardcore pro-Remain territory. Sturgeon and the SNP wants to keep Scotland in the EU. Given a chance, there is no way the Scottish parliament would vote for Brexit. So does Brexit breach the "devolved matters" requirement that would give Edinburgh the legal power to withhold its consent for Brexit?
Experts' opinions are mixed.
The House of Lords has received legal advice indicating that the UK government in Westminster would have to get a vote from the Scottish parliament in order to execute a Brexit:
"We asked Sir David [Edward] whether he thought the Scottish Parliament would have to give its consent to measures extinguishing the application of EU law in Scotland. He noted that such measures would entail amendment of section 29 of the Scotland Act 1998 [reaffirmed in the Scotland Act 2016], which binds the Scottish Parliament to act in a manner compatible with EU law, and he therefore believed that the Scottish Parliament's consent would be required."
Here is some more detail on that:
"Baroness Suttie: ... I have a specific question to Sir David, if I may. Do you think that the Scottish Parliament would be likely to grant legislative consent? If they did not, what would be the consequences?"
"Sir David Edward: The formal consequence is this. Under Section 29 of the Scotland Act 1998 the Scottish Parliament is bound by EU law, and, ditto, under Section 57(2) the Scottish Government are bound by EU law. Under the Scotland Bill [2016] that is going through Parliament at the moment, the Sewel convention will be recognised in Section 2 if it becomes an Act. Therefore, as I see it, you would have to amend the Scotland Act and, therefore, you would have to have legislative consent from the Scottish Parliament."
And the House of Lords Select Committee on Article 50 published this footnote, which strongly suggests that the consent of the Scottish Parliament would be required:
The key to the entire debate is the word "normally" in the text of the 2016 act. Some legal experts say that Brexit is not a "normal" circumstance and thus the UK government retains the power to legislate for Scotland. Westminster has always reserved that power for itself, although via devolution has allowed Scotland to conduct its own affairs.
Fiona Killen, a Partner at Anderson Strathern, believes that Scotland can't withhold its consent:
"However, both the Scotland Act 1998 (s28(8)) and the preceding convention contain the word "normally" in relation to circumstances in which the consent of the Scottish Parliament would be sought."
"As reflected in section 28(7) of the Scotland Act 1998, the devolution of power to Scotland was not an absolute transfer of power, but rather a sharing of power, with the UK Parliament retaining the absolute power to legislate in devolved areas. Section 28(8) remains subject to section 28(7) which states that "This section does not affect the power of the Parliament of the United Kingdom to make laws for Scotland"."
But it is complicated. Prof. Mark Elliott of the University of Cambridge thinks Scotland can't block Brexit. But he also previously argued that the government could trigger Article 50 through royal prerogative - and he turned out to be wrong about that, according to the recent High Court ruling on that issue.
Mark McKeown of law firm Turcan Connell believes the law is unclear. The UK Supreme Court may have to clear it up.