Introduction

Recently Texas governor Gregg Abbott openly defied the federal government over migration control. Echoing ‘the secessionist rhetoric’ of the Confederacy and Civil War Era, he claimed that the federal government ‘has broken the compact between the United States and the States’. This incident not only brings to light Texas’s various secessionist movements, such as ‘Texit’ (Texas Exit) or the ‘Republic of Texas’, but also prompts reflection on the seminal case of Texas v White. There, the US Supreme Court examined the legality of Texas’s attempted secession during the Civil War. In this article, I provide a brief contrast of how the Supreme Court of the United States (SCOTUS) perceived secessionism compared to the approach of the UK Supreme Court’s (UKSC) in the relatively recent case on the Scottish Independence Referendum Bill.

The purpose of this brief comparison is to highlight how the locus of sovereignty affects the complexity of the secessionism procedure as well as the dissolubility of the union itself. One point which the post drives home is that while parliamentary sovereignty is usually seen to indicate constitutional strength, comparing the two cases shows that parliamentary sovereignty may, with some caveats, indicate constitutional vulnerability. Specifically, the blog aims to demonstrate that, all other factors being equal, a union premised on parliamentary sovereignty can be more liable to secessionism from a legal and procedural standpoint compared to one premised on a shared sovereignty model. By adding a comparative lens to the Scottish Independence Referendum Bill case, the blog underscores the impact of different approaches to sovereignty on the resilience and fragility of constitutional unions.

Comparing the two cases on two questions: is the union dissoluble and who holds the constituent power to change it?

As is well-known, in the mid 19^th century, Texas and other Southern states rebelled and declared secession from the United States and formed a rival Confederate government. The constitutionality of this secession came into sharp relief in Texas v White. The case involved a claim to recover millions of dollars’ worth of United States bonds sold by the state of Texas during the Civil War. For the case to be admissible, it must have been filed by a US State and thus the case hinged on whether Texas remained ‘a state’ within the United States during the period of rebellion. As a logical prior to this question, the court had to examine whether Texas’s secession, decreed by state constitutional convention and ratified by a majority of its citizens, was legally valid. In doing so, the court provided insightful answers on two interrelated issues: the nature of the union and the locus of constituent power.

The Court unequivocally held that Texas’s secession was ‘absolutely null … utterly without operation in law.’ It ‘did not cease to be a State, nor her citizens to be citizens of the Union.’ The court reached this answer through blending constitutional text with theory. The Union between American states was found to be ‘indissoluble’ and ‘perpetual’ because the preamble of the Constitution provided that it was promulgated ‘in order to form a more perfect Union’. The court read ‘perfect union’ to entail that the  constitution created ‘an indestructible Union composed of indestructible States.’

The court briefly turned to the second issue of the locus of sovereignty and constituent power. If the preamble of the Constitution suggests that the Union is ‘indestructible’, the question then is whether the Constitution can be amended to allow a state to leave. The court answered that (aside from an extra-legal revolution), the only constitutional route was to amend the constitution. The federal constitution is upheld by states as co-holder of constituent power or ‘territorial subjects’ as Tierney terms them. Therefore, for a state to constitutionally secede, a constitutional amendment process must be initiated, which requires the consent not only of the federal legislature but also the ratification of three-fourths of the other states.

The two points of the indissolubility of the union and the process of constitutional change are starkly different in the Scottish referendum case. Here, the UK Supreme Court (UKSC) held that the Scottish Parliament did not have the competence to enact legislation to hold a second referendum on Scottish independence. The Court found the Scottish Bill’s purpose to be ultra vires because it related to the reserved matters of the ‘Union’ and the authority of the ‘UK Parliament’ over Scotland.  The case is well summarised elsewhere, and the goal here is not to re-summarise it, but rather to show how the UKSC addressed or bypassed the two issues of the nature of union and the locus of power and their impact on secessionism.

On the nature of the Union, the Court made no mention of the Union with Scotland being perpetual or indissoluble. Though the Court did discuss at various points in the judgment that the Bill’s ‘purpose’ is to ‘terminate’ Parliament’s sovereignty over Scotland, the court did not say or suggest that such sovereignty is not terminable, or that the Union is indestructible. Implying the dissolubility of the Union is understandable, and the post does not advocate that the UKSC should have declared the Union indissoluble. Rather, highlighting this underlying aspect of the Court’s approach serves a comparative purpose with the American case. Contrasting the divergent stance of the two courts can add insights on the different nature of the two constitutional systems. While the divisibility of sovereignty and the text of the entrenched US constitution made it easy for SCOTUS to reach its conclusion, the different nature of the UK constitution, as manifested in the issues discussed below, explains the different path towards the nature of union and secession.

First, whilst the Act of Union 1707 describes the union between England and Scotland as one of ‘perpetual foundation’ which shall ‘continue in all time coming’, the Scotland Act itself does not support the ‘Union indissolubility’ thesis: in contrast to the American Constitution, which explicitly describes the Union as ‘perfect’, the Scotland Act does not contain such language, nor does it characterise the Union as perpetual and indestructible. The statute remains silent on the perpetuity of the union. However, this is not the case for the perpetuity of Scottish institutions. Section 63A(1) of the Scotland Act provides that the Scottish Government and Parliament ‘are a permanent part of the United Kingdom’s constitutional arrangements.’ Nonetheless, this is quickly qualified by Section 63A(3), which acknowledges the possibility of abolishing these Scottish institutions through a referendum by the people of Scotland.

Second, for the Court to assert that the Union with Scotland is entrenched as perpetual and indestructible, it would require choosing one of the extensively debated and competing theories of parliamentary sovereignty. Namely, whether sovereignty is fully self-embracing (permitting complete termination of sovereignty) or partially self-embracing (where surrendering sovereignty over a particular territory is possible) or it is a continuing sovereignty (where any transfer of sovereignty is reversible). As is well-known, this theoretical question has consumed much ink in literature with regards to the independence of former dominions (see Goldsworthy, Oliver). The Supreme Court has usually and prudently avoided giving a conclusive answer as to which theory ought to prevail.

Third, there are plenty of cases where Parliament terminated its authority over former dominions, such as Australia and Canada among others.  Fourth, deeming the Union indissoluble would have to contend with the fact that there was a precedent of calling for an independence referendum in 2014 which was described by Lord Hodge in Moohan v Lord Advocate [2014] as follows: ‘the referendum is a very important political decision for both Scotland and the rest of the United Kingdom’. Fifth, the Northern Ireland Act 1998 explicitly recognises the possibility of terminating Parliament’s authority there. All these factors make the argument for the Union of 1707 being indestructible a challenging one to make, especially in comparison to the relative ease of making such a case in America.   

Now, let’s consider the second question regarding the locus of constituent power to carry out the necessary changes if Scotland is to be allowed to leave the United Kingdom. The Court did not explicitly address this question, perhaps because the answer is straightforward and flows from established authorities and past practice. As Tocqueville noted with approval from Dicey, in the UK the ‘Parliament is at once a legislative  and a constituent assembly’. Like former dominions, if Scotland or any other devolved nations or regions seeks to secede, it needs to obtain the approval of Parliament as the holder of constituent power and the legal sovereign to enact the necessary legal change. An additional contrast here is that in the UK, unlike America, other UK territorial units hold no share of the constituent power and thus have no say on the secession of another unit.

In summary, the two cases highlight two differences: the American Union is legally perpetual and indestructible, while a similar description would be difficult to apply straightforwardly to the British Union. Secondly, whereas the constituent power to amend the constitution to allow secession is scattered across states as territorial subject in the US, the constituent power is centralised within the UK Parliament. The differences stressed by the two cases are highlighted in the table below. The next question is whether these two differences matter for the possibility and constitutionality of secession.

U.S Integrative Federalism Texas v White [1869]	UK Devolution Scottish Referendum case [2022]
‘Perpetual’, ‘indissoluble, ‘indestructible’ union	There is mention of an indissoluble union
Constituent power needed to change the constitution and approve secession -> decentralised across different states	Constituent power -> centralised within Parliament
3/4 states as territorial subjects must approve the constitutional change required to allow Texas to leave	Other territorial units (NI & Wales) have no say on Scotland and vice versa

How far do the two differences matter for secession?

If we assume for the purpose of comparison that preserving the union in the two systems is a positive good and to ‘break up’ is a negative outcome to avoid, then to mitigate the risk of secessionism, there is probably some value in being able to straightforwardly label the union as indestructible. But more importantly, a significant part of secessionism lies in overcoming the ‘burdens of constitutional inertia’ and to meet the procedural requirement for secession. Having to convince or pressure one centralised body (such as the UK Parliament) is relatively less burdensome than having to secure the consent not only of the federal legislature, but also thirty-eight states with their various electoral processes. This in itself makes, all other factors being equal, the possibility of meeting this procedural threshold easier in the UK compared to the US.  A relevant remark from Dicey comes to mind here. In comparing the two systems, Dicey told us that ‘the sovereign is in a federal state [like America] a despot hard to rouse. He is not, like the English Parliament, an ever-wakeful legislator, but a monarch who slumbers and sleeps.’ When it comes to secessionism, the fact that the US sovereign is a deep sleeper and ‘hard to rouse’ makes the burden of inertia favour the legal status quo which disfavours change and secessionism.

Maybe we can illustrate this point further using a thought experiment which relies on another Diceyan remark. Dicey told us that the ‘originality’ of the American Framers was ‘exaggerated’.  To him, they just skilfully applied ‘the notions which they had inherited from English law’. Let’s imagine that the American framers decided to keep the English notion of parliamentary sovereignty and somehow reconciled it with federalism in a system which they called ‘Devolutionary America’. Assume that Texas is trying to secede from this fictional ‘devolutionary Union’. Would it be easier to secure the consent of one body (the central legislature), or as is the contemporary position, to secure the consent of the federal legislature is required in addition to thirty-eight state legislatures with their various electoral rules and different interests? The answer seems clear.

That being said, a few clarifications must be entered. First, the claimed advantages of divided sovereignty with regards to preventing secession are largely limited to integrative federal models where many states come together to form a larger polity. The number of players makes it more complex to secure the necessary consent. As per other smaller federations (termed devolutionary federalism) such as Belgium, the distinction with unitary systems or the UK might be blurred.

Second, it could be argued that constitutional rules and tidy conceptual theories do not shape secessionism as much as practical realities. This is true, but only partially so. The importance of the political reality and extra-legal means was even judicially underscored by US Supreme Court in Texas v White, where it recognised that the constitutional provision on the indissolubility of the union can be altered extralegally through ‘revolution’. However, constitutional rules remain relevant to the legitimacy as well as the possibility of secession. As Tushnet has recently argued, the structure and constitutional rules can alter the incentive calculus and dampen the momentum for secession. Bogdanor made a similar cautionary claim in surveying the role of legal overcentralisation and constitutional power imbalance in accelerating the breaking up of many unions across the world.

Conclusion

To conclude, comparing the two cases shows how the American Union was judicially labelled as ‘indestructible’, but a similar label would be difficult to apply to the United Kingdom. Considering the locus of constituent power, secessionism in the UK appears to be one constitutional step away, while in the US, it is thirty something steps away. This observation is not a call to depart from parliamentary sovereignty, but rather serves as a brief comparative insight which, like any comparison, aims to revisit assumptions and provide lessons for ‘self-reflection’ or, when necessary, ‘self-lamentation’.

Undoubtedly, a union premised on parliamentary sovereignty facilitates expansion as much it facilitates secession. However, since the US President Wilson preached self-determination in the aftermath of World War I, the global trend has leaned towards self-determination (and consequently secessionism) rather than expanding borders and integration. In such an era, having all constitutive eggs in one basket might carry slightly higher risks.

Dr Mohamed Moussa, Lecturer in Law, Murray Edwards College, University of Cambridge

(Suggested citation: M. Mousa, ‘From Texas to Scotland: Secessionism and the Vulnerability of Parliamentary Sovereignty’, U.K. Const. L. Blog (30 May 2024) (available at https://ukconstitutionallaw.org/))