It now seems certain that there will be a referendum on Scottish independence in the near future. This call for a referendum has thrown up a number of tricky constitutional issues: in particular, who can call a referendum, and the constitutional consequences of a yes vote. This post reflects on some of the legal and moral issues raised. One of the aspects of the debate that has been overlooked is the role of the United Kingdom constitution. If Scotland is to become a state, at least the first stage of this process should be undertaken through the constitutional structures of the United Kingdom. This is a legal requirement – these are the legal structures we possess, and ignoring them would cause avoidable problems – but also a moral requirement. The United Kingdom is responsible for the wellbeing of all its citizens – both within and outside Scotland. It is under a moral duty to ensure that the process towards secession is undertaken in a manner that is fair to all of its people. The United Kingdom, acting through the institutions of the state, must ensure that the Scottish people are given a chance to express their views in a fair referendum, and, if the vote is positive, that the new constitutional settlement is a just one.

(i) Who Can Hold a Referendum?

The initial question of which institution can hold a referendum has proved controversial. Alex Salmond, the Scottish First Minister, thinks it is the Scottish Parliament that decides when to hold the referendum and the question that should be set. David Cameron, the British Prime Minister, in contrast, regards these powers as vested in the United Kingdom Parliament: Parliament can delegate these powers to the Scottish Parliament, but can also impose limits on the exercise of this power if it chooses (see the consultation paper from the Scottish Office).

The answer to this constitutional conundrum is fairly simple. If the United Kingdom were a confederation like NATO or – perhaps – like the European Union, it would be a collection of sovereign states, each of which could leave the group at any time. If this were the case, the process by which Scotland could withdraw from the confederation would be determined by Scottish constitutional law. But the United Kingdom is not a confederation. The United Kingdom falls somewhere between a unitary state and a federation. In a unitary state any powers possessed by regional authorities are delegated to them from the centre, and can be revoked. The language of devolution and, indeed, the devolution statutes take this form. The Scottish Parliament has the power it has because of a statute of the United Kingdom Parliament, and, in law, the United Kingdom Parliament retains the capacity to remove these powers at any time. This narrow legal view obscures the constitutional reality of the Scottish Parliament’s position. In a federation both the federal level (for our purposes, the Westminster Parliament) and the state level (Scotland) have their own area of power, conferred on them by the constitution, that the other level cannot encroach upon: all levels of the state are constitutionally limited. In many respects the United Kingdom now looks more like a federal than a unitary state. The Sewel conventions limit the capacity of the United Kingdom Parliament to legislate for Scotland and the courts treat statutes of the Scottish Parliament as exercises of primary legislation, rather than the delegated legislation produced by local authorities and other bodies.

But whether we treat Scotland as part of a unitary state or a federation, the answer to the questions about the Scottish Parliament’s part in the independence process is clear. In both a unitary state and a federation questions of secession, the mechanisms by which a territory leaves the state, are resolved within the existing structures of the state. It is the state as whole that decides who gets to decide, and how that decision is made. The question about the Scottish Parliament’s capacity to hold a referendum and withdraw from the Union is answered by scrutiny of the law that empowers that body.

In some federal constitutions territories are given the power to leave the federation; they are given a right to secede. Looking at the statute that empowers the Scottish Parliament, it is plain that the Scottish Parliament has not been given this power. A quick glance at Schedule 5 of the Scotland Act 1998 makes this clear: the Scottish Parliament cannot pull Scotland out of the Union. Under the present constitution, decisions about Scottish independence are left with the United Kingdom Parliament.

Does this mean that the Scottish Parliament cannot hold a referendum on independence? Obviously not. The Scottish Parliament has wide powers, and can almost certainly run a referendum if it wishes. This referendum would not fall foul of matters reserved to Westminster in the Scotland Act because it would not be binding, and so would not, in itself, alter the legal relationship between Scotland and Westminster – though it might well affect the political pressure for some sort of change. Though this might well end up in the Supreme Court, it is likely that Alex Salmond is right: the Scottish Parliament can hold a referendum on independence. But it would only be an advisory referendum: it would be open to the United Kingdom Parliament to ignore the vote.

Could the Westminster Parliament hold a binding referendum on independence? The current proposal of the Westminster government is that the United Kingdom Parliament would confer on the Scottish Parliament a limited power to hold a referendum, but with certain limits on the question posed, and the time-frame in which the referendum would be held. If the argument in the previous paragraph is correct, and the Scottish Parliament could hold its own referendum, it might be hard to see why the proposal of the Westminster government should be preferred. There are two arguments that render this an attractive option. First, if independence happens it will amount to a divorce of Scotland from the rest of the United Kingdom. For the reasons discussed in the second part of this post, whilst this is a decision that the Scottish people make, it is for the United Kingdom to determine that the decision has been made fairly and clearly. Using the Westminster proposal would remove the risk of dispute following a referendum. Secondly, whilst the Scottish Parliament can only mount an advisory referendum, Westminster could hold a mandatory referendum: a yes vote would automatically begin the process of secession. This would clarify the issue, compelling supporters of independence to ask if they really did want this outcome, and – on the other hand – would remove the risk of backsliding by supporters of the union in Westminster after the vote.

Some might wonder what has become of parliamentary sovereignty in this story: can the Westminster Parliament be constrained by another entity, that is, the Scottish electorate? The old rule of parliamentary sovereignty appeared to bar limits on Parliament: whatever the queen-in-parliament enacted as statute was law. How, then, could Westminster be compelled to accept the outcome of a Scottish referendum? As I have argued elsewhere, the supposed rule of parliamentary sovereignty is a legal principle that was extinguished in the case of Factortame, when the House of Lords suspended an Act of Parliament that ran contrary to European Law. However, for those who still believe in parliamentary sovereignty a little clever constitutional navigating would allow us to steer around the rule.

A similar problem was addressed and dodged in the legislation establishing the referendum on the Alternative Vote. In the Parliamentary Voting System and Constituencies Act 2011, following a positive vote Ministers would have been obliged to bring into force the new voting system, set out in a schedule to the Act, without returning to Parliament for its approval. So, even though Parliament was not limited in law, and sovereignty was preserved, in practice it was constrained: having passed the 2011 Act, Parliament would not be given a chance to change its mind between the referendum and the proposed change to the law. The same model could be adopted in relation to Scotland. At the most extreme, Parliament could include in the referendum statute a provision conferring independence on Scotland, a provision that would automatically come into force following a positive referendum. For the reasons discussed in the next part of the post, this would be a little quick: even once it is decided that Scotland will become a sovereign state, this process should still take some time. A more sensible requirement would be that following a positive vote commissioners would be appointed to negotiate a secession agreement, and the Scottish Parliament would be empowered to establish a commission to draw up a draft constitution for Scotland. The product of these negotiations could either be rendered automatically binding or, more likely, a second statute of the United Kingdom Parliament would be required to approve the outcome of these processes.

(ii) The Role of the United Kingdom Parliament.

Some might be tempted to exclude the United Kingdom Parliament from the process of Scottish independence altogether – or, at least, minimize its role. However, there are a number of tasks that fall to the United Kingdom Parliament in the move towards Scottish independence. The United Kingdom, the state, is under a duty to look after the wellbeing of its members. This is a moral duty and, also, an aspect of the prerogative. When one part of the Union is considering secession, the United Kingdom should ensure that: first, it is appropriate to allow the territory to secede; second, that the process by which secession is decided is a fair one; third, that the new state will treat its new members properly; and, fourthly, that the basis of independence is fair to others within the Union.

The first question – whether it is appropriate for the territory to secede – is not relevant in Scotland’s case. Just about everyone accepts that Scotland is the type of territory that can properly gain state-hood if its people wish it. The willingness of the United Kingdom government to grant a binding referendum to Scotland is an express recognition of this. But it should not be thought that all territories within the United Kingdom enjoy this recognition. If the people of Oxford wanted to form a state, the United Kingdom should refuse to allow them to do so. This is too small a group to warrant state-hood: it could not effectively make the types of political decisions that are made at the level of the state. Bizarrely small states are unfair in two respects. First, they are unfair on their own members, who cannot exercise a share in control over many issues that affect them. They are reliant upon, and effectively subject to, their powerful neighbours or vulnerable to powerful private bodies. Secondly, they are unfair on members of the larger states that surround the smaller state, if members of the small state rely on the larger ones for protection, an educated labour-force, or other forms of support, without contributing to the running of that state.

The second question – the fairness of the process – is relevant to Scotland. The United Kingdom should ensure that both the question asked of the Scottish people and the manner of the campaign are fair. The question and process should, as far as possible, be neutral. This is important, because it could be that the phrasing of the question can influence the outcome of the vote. People may be more likely to support a positive call for a sovereign Scotland than support a negative call for the break-up of the Union. The question posed in the referendum should be chosen by an independent body, and should attempt to avoid phrasing that would influence the vote. Given the importance of the vote, the ballot should not include a third option – Alex Salmond’s preferred form – giving more power to the Scottish Parliament short of independence. A three-option referendum is undesirable because it will distract attention from the principle question of the Union and, more importantly, because it is likely to distort the votes for the third option. People who reject independence may be tempted to ‘compromise’ on the third option, even if they would not have voted for it in a straight referendum. The simplest solution would be, if the independence vote were lost, to hold a further referendum in a couple of years on increased power for the Scottish Parliament.

The third question – fairness for those within Scotland – also falls to the United Kingdom. As Scotland moves towards independence, the United Kingdom should ensure that minority groups within Scotland are protected, and the new structures of the Scottish state respect the basic principles of constitutionalism – democracy, the rule of law and so forth. The United Kingdom should also ensure that the new constitution of Scotland is the product of a range of groups from within Scotland: whilst the SNP’s draft constitution for Scotland could provide a starting point, other parties should also be involved in the process. It might be objected that there is no reason to suppose that this will not be the case: the SNP, the driver for independence, is already committed to many of these elements. But this overlooks the nature of the duty on the United Kingdom: this is not something the United Kingdom may do, but something it must do. Ultimately, the final decision about Scottish independence is made at the level of the Union. Just as it would be wrong – indeed, immoral – to refuse independence in many situations, it would also be wrong to grant it if proper constitutional structures were not in place.

An interesting question is whether a second referendum is needed before Scotland gains independence. Jo Murkens, writing for the Constitution Unit, argues that a second referendum is needed, to allow the people of Scotland a say in the final, negotiated, plan for independence. Just because the people of Scotland want independence, it does not necessary follow that they endorse independence on the terms negotiated. This point is reinforced when the draft constitution for Scotland is considered. This constitution would – presumably – be drawn up before independence. Some modern constitutions are put to the people to ratify. Would the Scottish constitution be put before the people? If so, this vote could stand as the second referendum: both an affirmation of the negotiating process, and an endorsement of Scotland’s new constitution.

Finally, the United Kingdom Parliament should ensure that the independence process is conducted in such a way as to be fair to those who will not become members of the Scottish state. Perhaps the most important aspect of this – a little discussed aspect – is the consequences of a negative vote in a referendum. If the Scottish people do not vote for independence, there needs to be a fixed, and reasonably lengthy, period of time set out before the referendum can be held again. In all states people in one part of the state sometimes lose out because of the interests of people in another part. This becomes a problem if one territory is continually on the verge of leaving. The fear is that one part of the state will take on burdens that will not, in the end, be balanced by burdens shouldered by that other part of the state, that they will leave before undertaking their share. People in the other parts of the United Kingdom need to know that a rejection of independence is a rejection for a significant period of time – perhaps as long as fifty years – if they are to be asked to make the kind of reciprocated sacrifices that are normal within a state.

There are also a plethora of smaller issues that need to be resolved before independence: the use of embassies, the army, access to watercourses, transport, the European Union etc. None of these presents an insurmountable problem, but they do require negotiation between representatives of Scotland and representatives of the remainder of the Union. Once again, this reinforces the need for the independence referendum to be consensual, accepted by the whole of the peoples of the United Kingdom.

For these reasons, it would be a mistake for the United Kingdom Parliament to tie itself to granting independence before the negotiations are complete. Following an affirmative referendum, independence for Scotland would become inevitable, but should follow a staged and negotiated process that would include the United Kingdom government and Parliament. The final stage of the independence process in the United Kingdom should be a statute of the Westminster Parliament that renders secession constitutional under the pre-existing United Kingdom constitution. It would then fall to Scotland to carry forward the project.

Nick Barber is a Fellow of Trinity College, Oxford.