Mr Styles' article commences:
"The use of the prerogative power to invoke Article 50 of the TEU has been much discussed since the Brexit vote on 23 June 2016 (including this initial post on the matter and a follow-up post). The present author believes that only an Act of Parliament can be used to invoke Article 50 but if I am mistaken then a very interesting route to Scottish independence potentially opens up.
If the UK government were to persist in arguing that the Prerogative can be used to trigger Article 50 and that submission were to be upheld by the courts then that will logically lead to a conclusion that Westminster will not welcome: that the Prerogative can be used to dissolve the Union between Scotland and England."
If correct in law, this would be a startling consequence.
At the present time, legal action has been commenced in London and in Belfast on the question of whether prerogative may be used. I am not aware of any similar case in the Scottish courts.
In common with Mr Styles and several other commentators, I think that an Act of Parliament ought to be used to permit Ministers to trigger Article 50 but I readily acknowledge that there is a strong case to the contrary. My earlier post is here. Whatever the outcome of the litigation, the legal accuracy of the Aberdeen article must be doubtful. Here are my reasons.
I will refer to the article as "the Styles argument" or "the argument."
1. The argument notes that the Union between England and Scotland was preceded, in 1706, by Articles of Union. This is a matter of historical record and the process of negotiating the Articles is helpfully set out by the UK Parliament. The Articles amount to a Treaty between what were then two separate nations although they shared a single monarch from 1603. A Treaty alone could not alter the law in either Scotland or England. Acts of what were then the separate Parliaments of Scotland and England were needed to to do that.
2. The separate Parliaments of Scotland and England each enacted legislation in accordance with their own procedures - the Union with England Act 1707 and the Union with Scotland Act 1706 It was this legislation which created a new nation being the UNION known as Great Britain and there has never been any question over the validity of the legislation.
3. Points 1 and 2 are supported in an article by David M Walker (Regius Professor of Law, University of Glasgow 1958-90) - Journalonline - The Union and the law - 18th June 2007
4. The Styles argument next asserts that - "If it is correct that the mere use of the Royal Prerogative is sufficient legal authority to trigger Article 50 of the TEU and so revoke and repeal the European Communities Act 1972 then it would seem to follow by analogy that the Royal Prerogative could be used in the context of Scotland leaving the UK ...."
What is the true effect of Article 50? Triggering Art 50 will NOT revoke and repeal the European Communities Act 1972. though, in fairness, it will commence a process that could, ultimately, require Parliament to enact legislation to repeal the 1972 Act. All that Art 50 will do is to commence the process of negotiation leading to Brexit.
5. The argument then claims that Article 50 is part of domestic law - " ... Article 50 which is not an international treaty but part of the domestic law."
Article 50 of the TEU binds the United Kingdom in international law but it is going too far to say that it is part of domestic law. The European Communities Act 1972 ensures that certain directly applicable EU legislation takes effect in domestic law without further domestic enactment - section 2(1). Section 2(2) of the Act enables the making of legislation to give effect in domestic law to other EU obligations such as those in EU Directives. The Act also requires judicial notice to be taken of the Treaties (section 3) and, in any legal proceedings, the meaning of any of the Treaties is a question of law. Furthermore, under the law as developed by the Court of Justice of the EU, certain Treaty articles are capable of having direct effect in national law provided that certain conditions are met. That is, I think, as far as the ECA 1972 goes and it therefore stops short of a lock, stock and barrel incorporation of the Treaties into domestic law.
6. It is well established law in the jurisprudence of both England and Scotland that prerogative powers are subject to statute law. Prerogative powers may be abolished or replaced by Acts of Parliament. In other instances, Parliament has enacted statutory powers but left the prerogative power intact. Where there is overlap, Ministers must use the statutory power - see Attorney-General v De Keysers Royal Hotel  AC 508. See also R v Home Secretary ex parte Fire Brigades Union  2 AC 513.
7. The Crown (i.e. the monarchy) of both England and Scotland has been vested in the same person since 1603 (King James VI of Scotland and James I of England) - see Union of the Crowns.
Since 1707 when the Union was formed, there is a single Crown for the whole of Great Britain. (Interestingly, the symbolic Honours of Scotland are used on certain ceremonial occasions in Scotland).
8. The Acts of Union created a single nation (Great Britain) and a single national Parliament. There is an argument that the Articles of Union (i.e. the Treaty) cannot be legally discontinued. Professor Walker wrote this (see the link in 3 above) - "There appears to be neither authority nor precedent for Parliament interfering with an international treaty, particularly where under the treaty the consenting states had ceased to be independent states and had merged their personalities in a new state by an incorporating union."
For my part, I think this is a case where, if the UK parliament wished to alter matters then political reality will trump any contrary legal theory! If Professor Walker is correct then it is difficult to see how Scottish Independence could be achieved! Whenever Scottish Independence is mentioned there never seems to be any doubt that, legally-speaking, it can be achieved. Whether it is politically desirable is a matter on which opinion differs markedly but that is altogether another issue.
9. The Styles argument proceeds to say that it could be possible for the Scottish First Minister to use prerogative power to revoke the Articles of Union and thence by implied repeal revoke the Act of Union.
Styles notes that the Union of the Kingdoms of Scotland and England is a reserved matter (Scotland Act 1998 Schedule 5 Part I) but Her Majesty's prerogative is not reserved. The argument thus concludes that there seems nothing in law to prevent the Scottish Government exercising their Prerogative powers to revoke the Articles of Union and hence the Act of Union.
Two observations on this:
a) It cannot be the case that the Scottish government could revoke the Articles of Union using prerogative because the provision that Her Majesty's prerogative is not reserved has to be read in the context of Schedule 5 also stating very clearly that the Union is a reserved matter. The Union is not within the legislative competence of the Scottish Parliament. Therefore, it cannot have been the intention of the UK Parliament, when enacting the Scotland Act 1998, to have made it possible for Scottish Ministers to simply achieve by prerogative powers what they are not permitted to achieve by legislation.
b) The Articles were negotiated on behalf of two nations which gave up their independent existence to form the Union. It is therefore inconceivable that, over 300 years later, either Scotland or England could simply revoke the Articles of Union using prerogative power though it would be possible for the UK Parliament to enact legislation rendering the Articles ineffective for the future.
The Styles argument is interesting but, with the greatest of respect, for the above reasons I do not think it is correct.
As ever, comment is welcome.