AXA General Insurance v The Lord Advocate  UKSC 46;  1 AC 868
Lord Hope ......
The common law grounds
 The appellants' case at common law is that the 2009 Act was the result of an unreasonable, irrational and arbitrary exercise of the legislative authority conferred by the Scotland Act 1998 on the Scottish Parliament. Although the Dean of Faculty did not abandon that argument in this court, he accepted that if his argument that the Act was incompatible with A1P1 were to be rejected on the grounds that there was a legitimate aim and that its provisions were reasonably proportionate to the aim sought to be realised he could not succeed on this ground at common law. On one view, very little more need be said about it. But the question as to whether Acts of the Scottish Parliament and measures passed under devolved powers by the legislatures in Wales and Northern Ireland are amenable to judicial review, and if so on what grounds, is a matter of very great constitutional importance. It goes to the root of the relationship between the democratically elected legislatures and the judiciary. At issue is the part which the rule of law itself has to play in setting the boundaries of this relationship. I think therefore that the argument which this part of the appellants' case raises cannot be dismissed so easily.
 The issue can be broken down into its component parts in this way. First, there is the question whether measures passed by the devolved legislatures are amenable to judicial review, other than in the respects expressly provided for by the devolution statutes, at all. If not, that will be the end of the argument. But if they are open to judicial review on common law grounds at all, there is the question as to what these grounds are. At the one extreme are the grounds that the appellants' second plea in law encapsulates: that the legislation is unreasonable, irrational or arbitrary. At the other is the proposition that judicial intervention is admissible only in the exceptional circumstances that Lord Steyn had in mind in R (Jackson) v Attorney General  1 AC 262 , para 102; see also my own speech at paras 104-107 and Baroness Hale of Richmond's observations at para 159. To answer these questions in their proper context it is necessary to set out the background in a little more detail. Although I am conscious of the implications of what the court decides in this case for the other devolved legislatures, I shall concentrate on the position of the Scottish Parliament. As was common ground before us, I consider that, while there are some differences of detail between the Scotland Act 1998 and the corresponding legislation for Wales and Northern Ireland, these differences do not matter for present purposes. The essential nature of the legislatures that the legislation has created in each case is the same.
 The starting point for an examination of the first question is the following proposition in West v Secretary of State for Scotland 1992 SC 385 , 412-413:
"The Court of Session has power, in the exercise of its supervisory jurisdiction, to regulate the process by which decisions are taken by any person or body to whom a jurisdiction, power or authority has been delegated or entrusted by statute, agreement or any other instrument."
 Devolution is an exercise of its law-making power by the United Kingdom Parliament at Westminster. It is a process of delegation by which, among other things, a power to legislate in areas that have not been reserved to the United Kingdom Parliament may be exercised by the devolved legislatures. The Scotland Act 1998 sets out the effect of the arrangement as it affects Scotland with admirable clarity. Section 1(1) of the Act declares: "There shall be a Scottish Parliament." Its democratic legitimacy is enshrined in the provisions of section 1(2) and section 1(3) , which provide for the election of those who are to serve as its members as constituency members and by a system of proportional representation chosen from the regional lists. Section 28(1) provides that the Parliament may make laws, to be known as Acts of the Scottish Parliament, and section 28(2) provides for them to receive the Royal Assent. Section 28(5) provides that the validity of an Act of the Scottish Parliament is not affected by any invalidity in the proceedings of the Parliament leading to its enactment. Although section 28(7) provides that that section shall not affect the power of the United Kingdom to make laws for Scotland, in practice the Scottish Parliament enjoys the same law making powers for Scotland as the Westminster Parliament except as provided expressly for in section 29 which, in certain closely defined respects, limits its legislative competence. Section 29 does not, however, bear to be a complete or comprehensive statement of limitations on the powers of the Parliament. The Act as a whole has not adopted that approach: see Somerville v Scottish Ministers (HM Advocate General for Scotland intervening)  1 WLR 2734 , para 28.
 The carefully chosen language in which these provisions are expressed is not as important as the general message that the words convey. The Scottish Parliament takes its place under our constitutional arrangements as a self-standing democratically elected legislature. Its democratic mandate to make laws for the people of Scotland is beyond question. Acts that the Scottish Parliament enacts which are within its legislative competence enjoy, in that respect, the highest legal authority. The United Kingdom Parliament has vested in the Scottish Parliament the authority to make laws that are within its devolved competence. It is nevertheless a body to which decision making powers have been delegated. And it does not enjoy the sovereignty of the Crown in Parliament that, as Lord Bingham of Cornhill said in Jackson , para 9, is the bedrock of the British constitution. Sovereignty remains with the United Kingdom Parliament. The Scottish Parliament's power to legislate is not unconstrained. It cannot make or unmake any law it wishes. Section 29(1) declares 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. Then there is the role which has been conferred upon this court by the statute, if called upon to do so, to judge whether or not Acts of the Parliament are within its legislative competence: see section 33(1) and paragraphs 32 and 33 of Schedule 6 , as amended by section 40 and paragraphs 96 and 106 of Schedule 9 to the Constitutional Reform Act 2005 . The question whether an Act of the Scottish Parliament is within the competence of the Scottish Parliament is also a devolution issue within the meaning of paragraph 1(a) of Schedule 6 to the Scotland Act 1998 in respect of which proceedings such as this may be brought in the Scottish courts.
 Against this background, as there is no provision in the Scotland Act which excludes this possibility, I think that it must follow that in principle Acts of the Scottish Parliament are amenable to the supervisory jurisdiction of the Court of Session at common law. The much more important question is what the grounds are, if any, on which they may be subjected to review.
 There is very little guidance as to how this question should be answered in the authorities. I do not think that we get much help from cases such as R v Secretary of the State for the Environment, Ex p Nottinghamshire County Council  AC 240 , R v Secretary of State for the Environment, Ex p Hammersmith and Fulham London Borough Council  1 AC 521 and City of Edinburgh District Council v Secretary of State for Scotland 1985 SC 261 . They were concerned with the exercise of delegated powers by ministers and, as the judges of the First Division said, 2011 SLT 439, para 83, none of them is directly in point in this case. All I would take from them is that, even in these cases, a high threshold has been set. I also think that the situation that was considered in R (Asif Javed) v Secretary of State for the Home Department  QB 129 which was concerned with a draft order which was laid by the Secretary of State and approved by both Houses of Parliament is so different from that which arises here that it can safely be left on one side. The fact is that, as a challenge to primary legislation at common law was simply impossible while the only legislature was the sovereign Parliament of the United Kingdom at Westminster, we are in this case in uncharted territory. The issue has to be addressed as one of principle.
 The dominant characteristic of the Scottish Parliament is its firm rooting in the traditions of a universal democracy. It draws its strength from the electorate. While the judges, who are not elected, are best placed to protect the rights of the individual, including those who are ignored or despised by the majority, the elected members of a legislature of this kind are best placed to judge what is in the country's best interests as a whole. A sovereign Parliament is, according to the traditional view, immune from judicial scrutiny because it is protected by the principle of sovereignty. But it shares with the devolved legislatures, which are not sovereign, the advantages that flow from the depth and width of the experience of its elected members and the mandate that has been given to them by the electorate. This suggests that the judges should intervene, if at all, only in the most exceptional circumstances. As Lord Bingham of Cornhill said in R (Countryside Alliance) v Attorney General  AC 719 , para 45, the democratic process is liable to be subverted if, on a question of political or moral judgment, opponents of an Act achieve through the courts what they could not achieve through Parliament.
 The question whether the principle of the sovereignty of the United Kingdom Parliament is absolute or may be subject to limitation in exceptional circumstances is still under discussion. For Lord Bingham, writing extrajudicially, the principle is fundamental and in his opinion, as the judges did not by themselves establish the principle, it was not open to them to change it: The Rule of Law (2010), p 167. Lord Neuberger of Abbotsbury, in his Lord Alexander of Weedon lecture, "Who are the masters Now?" (6 April 2011), said at para 73 that, although the judges had a vital role to play in protecting individuals against the abuses and excess of an increasingly powerful executive, the judges could not go against the will of Parliament as expressed through a statute. Lord Steyn on the other hand recalled at the outset of his speech in Jackson , para 71, the warning that Lord Hailsham of St Marylebone gave in The Dilemma of Democracy (1978), p 126 about the dominance of a government elected with a large majority over Parliament. This process, he said, had continued and strengthened inexorably since Lord Hailsham warned of its dangers. This was the context in which he said in para 102 that the Supreme Court might have to consider whether judicial review or the ordinary role of the courts was a constitutional fundamental which even a sovereign Parliament acting at the behest of a complaisant House of Commons could not abolish.
 We do not need, in this case, to resolve the question how these conflicting views about the relationship between the rule of law and the sovereignty of the United Kingdom Parliament may be reconciled. The fact that we are dealing here with a legislature that is not sovereign relieves us of that responsibility. It also makes our task that much easier. In our case the rule of law does not have to compete with the principle of sovereignty. As I said in Jackson , para 107, the rule of law enforced by the courts is the ultimate controlling factor on which our constitution is based. I would take that to be, for the purposes of this case, the guiding principle. Can it be said, then, that Lord Steyn's endorsement of Lord Hailsham's warning about the dominance over Parliament of a government elected with a large majority has no bearing because such a thing could never happen in the devolved legislatures? I am not prepared to make that assumption. We now have in Scotland a government which enjoys a large majority in the Scottish Parliament. Its party dominates the only chamber in that Parliament and the committees by which bills that are in progress are scrutinised. It is not entirely unthinkable that a government which has that power may seek to use it to abolish judicial review or to diminish the role of the courts in protecting the interests of the individual. Whether this is likely to happen is not the point. It is enough that it might conceivably do so. The rule of law requires that the judges must retain the power to insist that legislation of that extreme kind is not law which the courts will recognise.
 As for the appellants' common law case, I would hold, in agreement with the judges in the Inner House (2011 SLT 439, para 88), that Acts of the Scottish Parliament are not subject to judicial review at common law on the grounds of irrationality, unreasonableness or arbitrariness. This is not needed, as there is already a statutory limit on the Parliament's legislative competence if a provision is incompatible with any of the Convention rights: section 29(2)(d) of the Scotland Act 1998 . But it would also be quite wrong for the judges to substitute their views on these issues for the considered judgment of a democratically elected legislature unless authorised to do so, as in the case of the Convention rights, by the constitutional framework laid down by the United Kingdom Parliament.