This disagreement can be illustrated in part by a recent statement he made on Twitter. Today the Scottish Parliament, with the support of the MSPs from the minority SNP Scottish Government and those of the Scottish Green Party, voted by a majority of 69 to 59 in favour of a motion. That motion formally requests that the Westminster Parliament should pass enabling legislation, which would authorise the Scottish Parliament to legislate for a second independence referendum. It indicates that the most suitable moment for that to take place would be between the conclusion of a proposed UK Brexit deal and the elapsing of the 2-year time period after which the UK regardless ceases to be in the EU. This would be between autumn 2018 and spring 2019.
Clarifying the disagreement
Adam takes the view that a referendum should not be held during that period. On the merits, I tentatively take the view that that timetable has no real advantage over a referendum held in 2020 or 2021, from just about anyone's perspective. Scotland will be taken out of the EU as part of the UK regardless, even if temporarily, under that timescale. Where I disagree with him is what the constitutional process should be for deciding whether and how an independence referendum should be held.
His argument is that:
"Lawful, fair secession referendums are an act of statecraft. Different countries do them differently. In the UK we do them by agreement. Here, it's not for one side unilaterally to demand a secession referendum. Timing, and other matters, must proceed by agreement. This would be the case whether or not the losing side last time had vowed that such votes are "once in a generation""I may well be drawing unfair inferences from this argument, but I don't think it takes us very far. Purely descriptively, he is correct, in my view, that as a matter of law a referendum cannot be legislated for on Scottish independence without explicit authorisation of the Westminster Parliament. This authorisation, legally, must take place either by way of primary legislation or under a "s30 Order" relaxing the range of devolved matters of the Scottish Parliament. On this point, then, I take his side rather than that of other Scottish legal academics, who argued last time that the Scottish Parliament might not need that consent, because they disagreed that a Referendum Bill would "relate to reserved matters".
The problem here is that this legal starting point tells us almost nothing about who should be allowed to call a secession referendum and in what circumstances, which is the nub of what people are actually and substantively disagreeing about. It also does not tell us anything about what principles should govern when legislatures should be prevented from authorising those referendums. We have no answer to the normative question as to how the process ought to go forward, or not go forward. We have only a shell, unless we are to infer from the default position of the Scotland Act that the intention is to confer a veto power on the Westminster Parliament. If we believe it should have a veto, we must squarely confront the reasons that it should have that veto: what interests is this veto designed to protect, and is the veto necessary to protect those interests?
The UK "approach"
Adam maintains that constitutional practice in the UK requires that referendums on secession should only take place "by agreement". This is a strongly contestable claim and one that is wanting for precision (though the standard disclaimer of "Twitter only allows 140 characters" does of course apply). He also says that our constitutional practice is different from other countries (one example might be Canada, where provinces have no legal bar on a referendum) though this is a descriptive observation; not a normative justification.
One reason Adam's descriptive claim is contestable that he is basing this position on, specifically, the way the 2014 referendum was held for Scotland, and not on the basis of a UK-wide constitutional norm. The Scottish Parliament had no say, for example, over whether and subject to what conditions the UK's secession referendum from the European Union should be held. It is not obvious that the UK Parliament should have power over a referendum on, say, an area normally falling within the competence of a devolved legislature either: there is clearly something unspoken here that is regarded as special to secession referendums.
Any referendum on the holding of a border poll for Northern Ireland to decide whether they should become part of Ireland is not subject to intergovernmental negotiation; on the contrary, there is a legal duty on the part of the Secretary of State for Northern Ireland if it appears likely to him that a majority of those in Northern Ireland wish to leave the UK and become part of the Irish Republic. He is legally required so to act, even if the majority of those elected at Stormont are against the holding of such a poll. Although the National Assembly of Wales would also probably not have the competence to hold a secession referendum, the scheme under which it has devolved powers is completely different from that of Scotland and it does not have the same kinds of restriction.
Moreover, other territories with a UK relationship have completely different norms that govern the circumstances in which secession referendums may be held. Gibraltar and the Falklands Islands, for example, do not need Westminster consent to hold a referendum on secession. When the UK refused to recognise the Western Australia secession referendum of 1933, it was not because it had denied dominions the right to hold such plebiscites, but because the Commonwealth of Australia itself had refused Western Australia that power.
My point here is that, if we are talking about strict constitutional law, the UK has no common method of settling this question at all. The Edinburgh Agreement was merely one way of ensuring a fair and legal referendum was held; it's not the only way and it's not a norm that we have to abide by.
What norms do we have?
But if you do think it is a norm we should abide by, I think we have to be much clearer about what it involved, what norms and precedents it set and whether those norms are and ought to be legal or merely in some looser sense constitutional. We would need compelling reasons, constitutional reasons, not just political ones, to depart from the approach we took last time.
Adam says that "it's not for one side unilaterally to demand a secession referendum". But who are the "sides" here? Do we mean it's not for one Government or for one Parliament so to demand? Or do we mean political parties or caucuses? This is important if we are making normative claims about what, constitutionally, should happen. What has happened here is that the Holyrood Parliament has "demanded" the power to hold a referendum, though it is not acting "unilaterally" in the sense that it is not (yet) purporting to hold a referendum without the necessary legislative consent of the UK Parliament. The Members of the Scottish Parliament who oppose the holding of a second referendum have a different constitutional role from that of the UK Government or the Members of the UK Parliament, even though they may, many of them, share party allegiances. The question "should a referendum be held" is not the same as the question "should the Scottish Parliament be allowed to hold a referendum".
The failure to treat those questions as distinct fudges this debate considerably. It would be constitutionally consistent for Unionist parties to say that the Scottish Parliament should be allowed to decide whether or not to hold a referendum, without saying that they believe such a referendum should be held. They may look politically inconsistent if they vote for one but against another, but political deftness is not a defence for eschewing constitutional norms.
If Adam and others are of the view that the Edinburgh Agreement provides a framework or precedent for how we should proceed, we need to look behind the mere fact of disagreement about whether a referendum should be held and to look instead at what constitutional principles guided the conclusions of the UK Government last time to accept that a referendum should be permitted to be held by the Scottish Parliament. There are two clues to what drove this. The first is the acceptance of the existence of a political mandate to hold a referendum. Bluntly, we need to be clear exactly what the minimum thresholds are here. Is it sufficient for the Scottish Parliament to vote in favour of either having or exercising the power to create a constitutional duty to take steps to enable that to happen? If not, why not? And what additional expectations or qualifiers, constitutionally, are we insisting upon, and why? The second is how we establish the existence of a political mandate to give effect to other constitutional norms, particularly conventions.
Constitutionally, the UK is quite opaque about what constitutes a political mandate for the purposes of constitutional conventions that guide the behaviour of legislatures and governments without courts getting involved. The Salisbury-Addison Convention refers to proposals contained in the governing party's manifesto, for instance, but it provides little if any guidance on what should happen in the event of minority or coalition government. The UK Parliament did publish a Joint Report of the Commons and Lords into constitutional conventions in October 2006, in which precisely this issue was raised, but there was disagreement as to its scope.
On one view as long as a party is able to form a government commanding the confidence of the Commons, Salisbury-Addison applies; on another it only applies to outright majority governments. The honest truth is we do not have a coherent set of principles to explain how and to what extent this convention concerning the existence of a "political mandate" transfers, if at all, from Westminster to Holyrood, given that the relationship between Commons and Lords is very different from Westminster and Holyrood. It is our "best guess" but nothing more than that. This lack of clarity means we do not have a clear answer about what to do with a minority Holyrood government on an issue, even where enough support from opposition parties is gathered to gain support behind a manifesto proposal. The UK Government opposed the holding of a Scottish referendum before 2011 in the absence of a Holyrood mandate: what was it about that Holyrood election that changed things? How do we decide that a referendum should be allowed to happen is not the same as asking how we decide whether a referendum should happen.
What must be agreed and by whom?
The Edinburgh Agreement itself did impose limits and restrictions on the manner of the exercise of a referendum power. It placed a time limit on its exercise, but did not prescribe a date. It limited it to a binary question, but did not prescribe a wording. It prescribed some of the rules and institutions applicable to the referendum, but did not set its franchise or dictate its campaigning rules.
The Edinburgh Agreement, insofar as it articulated principles at all, said that most of these matters were "for the Scottish Parliament to determine". If "agreement" is the basis on which secession referendums is to be held, and we base that principle on the constitutional practice of the Edinburgh Agreement, we must surely also take into account the constitutional practice of that agreement too? If a second referendum is to be held, we need compelling reasons other than political expediency for explaining why the UK Government should have more of a say over the terms of such a power than it did last time around.
This, in my view, means that it would be constitutionally inappropriate (though clearly not legally incompetent) for the UK Government to use its position in the UK Parliament to insist upon controlling the franchise of a second referendum. There seems to me to be no logical nexus between who may vote in the referendum and whether or not it should be held. It would also be very suspect, save to exclude ambiguity or bias, if they were to insist on a role in setting the question beyond making it a binary choice. It would in any case be logical on the Scottish Government's part for pragmatic reasons to use the same question as last time given the Electoral Commission said it was intelligible and not biased.
The only area in respect of which the UK Government is arguably on firmer ground is with respect to the timing around which a power may be exercised by the Scottish Parliament. Even then, we need a constitutional argument for why a power over timing justifies an outright veto over whether a referendum should be held at all. Put simply, what constitutional principles are protected by letting the UK Government determine when, at all, the Scottish Parliament can hold a referendum? This question is, again, not the same as the question when should the Scottish Parliament hold a referendum.
This question also breaks-down into a further inquiry: what kinds of control over the timing are necessary to protect fundamental constitutional interests? Should the UK Government be allowed, in extremis, to dictate the date? Should they be allowed to impose a time limit? Should they be allowed to impose a minimum waiting period? If there are additional concerns about a referendum taking place during a time of constitutional uncertainty (with Brexit negotiations) or that one is held too soon after a previous one, just what, in the terms Adam puts it, is it that has to be "done by agreement" between Governments and Parliaments, and what it is that has merely to be "done by agreement" between Members of the Scottish Parliament? What aspects of this process can the Scottish Parliament not be trusted to get right?
These are questions that the UK Government have not answered. If a power on restricting the timing of a referendum is not itself one that is subjected to checks and balances, it is in essence a legal veto. That is a drastic position that should demand clear constitutional justification, not just a descriptive statement of constitutional fact.
Saying that referendums must proceed by agreement does not tell us how they ought to proceed, and it does not tell us what constraints ought to apply, what it is reasonable to insist upon and what we should do if people cannot agree. Without those constraints referendums aren't "only held by agreement" at all. You are instead giving a partisan veto to a political institution dominated, structurally, by pro-Union politicians, and you have to provide a constitutional, not just a political, defence for that.
I do not think it is sustainable to make a constitutional argument against Holyrood being entitled to legislate for a second referendum on Sturgeon's timescale unless you reject, and reject openly, honestly and clearly, the notion that whether or not Scotland should be an independent country is ultimately a decision that should be for the Scottish people to choose or not to choose to take. It involves the rejection of the Claim of Right, the political articulation of the idea that the UK is a union constitution, not a unitary one, and that it is the sovereign right of the Scottish people to determine the form of government suited to their needs. The Scottish Parliament is the only democratically elected legislature that provides a representative basis for an expression of the will of the Scottish people.
And you know what? It's fine to reject that. But given it is the sentiment upon which much of the political legitimacy for the devolution settlement rests, good luck with that.