Parliamentary sovereignty has traditionally been understood to mean that Parliament is free to enact legislation on any area of law that it chooses, and that Acts of the U.K. Parliament take precedence over subordinate legislation, regulation, or common law rule. Understood this way, parliamentary sovereignty is a constitutional principle that is couched explicitly in legal terms: it is a legal principle with legal effect, speaking to other legal entities within our constitutional order regarding how they are to exercise their legal functions in light of legislation passed by Parliament. In essence, it is a doctrine of legislative supremacy which honours Parliament’s constitutional role by according its enactments their due authority. On this view, no discernible distinction exists between parliamentary sovereignty and Parliament’s law-making powers because sovereignty describes the scope and weight of those very powers.
A central feature of the political aspect of our constitution is that the other elements of legislative creation remain firmly within the purview of politics. The background circumstances which lead members of Parliament to vote for or against the enactment of legislation have been understood to fall outwith the concern of the judiciary. It is not for a court of law to question why Parliament has come to enact the legislation that it enacts or to refrain from acting when given the opportunity to. Such political circumstances do not affect the validity or authority of legislation, nor have political circumstances that affect parliamentary action or inaction been understood to undermine sovereignty. So long as Parliament is legally uninhibited in its creation of statute, it is sovereign. What courts are to do in their interpretation and application of legislation is another question entirely. There very well may be limits to how a court interprets legislation, given background constitutional principles such as the rule of law and the separation of powers, but this is a separate issue from how we make sense of the political aspects of our constitution.
Recent jurisprudence has called this picture into question. R (Miller) v Prime Minister marked an important shift in how the Supreme Court understands the relationship between the legal and political aspects of our constitution. In Miller II, the court held that an attempt to prorogue Parliament for a period of several weeks unduly affected the ability of Parliament to carry out its constitutional function of holding the government to account and so, with no reasonable excuse offered in explanation, was unlawful. The Inner House of the Court of Session had considered the exercise of prerogative power in this instance to be unlawful on the ground that it had been used improperly to ‘stymie’ Parliament from exercising its constitutional functions. In contrast, and despite widespread speculation that this was indeed the motive and purpose of prorogation, the Supreme Court chose instead to focus on its effects:
‘[A] decision to prorogue Parliament (or to advise the monarch to prorogue Parliament) will be unlawful if the prorogation has the effect of frustrating or preventing, without reasonable justification, the ability of Parliament to carry out its constitutional functions as a legislature and as the body responsible for the supervision of the executive. In such a situation, the court will intervene if the effect is sufficiently serious to justify such an exceptional course.’ 
This conclusion is grounded in both the principle of parliamentary sovereignty and what the court referred to as ‘parliamentary accountability’, the principle that the executive is accountable to Parliament for its actions and inactions.
The use of these principles and the connection drawn between them in this case has been subject to trenchant critique. Loughlin, for example, argues that in order for the court to conclude as it did, it needed to ‘transform a formal principle into a functional principle’. We can see from the judgment how one might conclude this. The Court, having orthodoxly described parliamentary sovereignty as the principle that ‘laws enacted by the Crown in Parliament are the supreme form of law in our legal system, with which everyone, including Government, must comply’ , stressed that this principle entails other principles demanding its efficacy.
Elliott helpfully provides several examples of these penumbral principles: the principle, established in the 17th century by the Case of Proclamations, that prerogative power cannot be used incompatibly with legislation enacted by Parliament; the De Keyser principle that prerogative cannot be relied on when the matter in question is governed by statute; the principle that Parliament cannot bind its successors; and the principle, recently applied in Privacy International but advanced by Laws LJ in Cart, that parliamentary sovereignty necessarily implies access to courts where authoritative judicial interpretation of statute must occur if Parliament is to have the capacity to enact effective law. Far from being a formal principle, concerned only with the authority of statute within a hierarchy of legal sources, parliamentary sovereignty has always had a functional element to it.
In Miller II, the Court drew out another principle from parliamentary sovereignty: that it ‘would … be undermined as the foundational principle of our constitution if the executive could, through the use of the prerogative, prevent Parliament from exercising its legislative authority for as long as it pleased’ . This seems to be a wholly defensible extension of the principle of sovereignty, understood not in purely formal terms, but as reflecting what it has always been: a principle protecting Parliament’s capacity to exercise its legislative function in a manner which is legally unimpeded by the prerogative.
This being said, recent judicial analysis of parliamentary sovereignty threatens to expand the concept beyond what is reasonable, unduly encroaching upon both the judicial and the political sphere. In Reference by the Attorney General and the Advocate General for Scotland – United Nations Convention on the Rights of the Child (Incorporation) (Scotland) Bill the court continued the expansion of the principle of parliamentary sovereignty in two important respects.
Firstly, it claimed that ‘A provision which required the courts to modify the meaning and effect of legislation enacted by Parliament would plainly impose a qualification upon its legislative power’ . While this statement referred to s 19 of the UNCRC Bill, an analogue was drawn with s 3 of the Human Rights Act which requires courts, as far as possible, to interpret statutes compatibly with Convention rights. This case turned on whether interpretative obligations and declarations of incompatibility limit the ability of Parliament to legislate. Given that the provisions under dispute in this case were modelled after analogous sections in the HRA and the fact that it was set out explicitly in the Explanatory Notes to the Bill that the intention of the Scottish Parliament was to replicate sections in the HRA, the Court was required to comment on these provisions too.
Unless the Court presumes that s 3 HRA cannot be repealed or an explicit exemption included within legislation, it is unclear how it qualifies the legal ability of Parliament to legislate. This provision, itself a product of Parliament’s ability to legislate, is directed towards the judiciary, influencing how courts are to interpret statute. It does not affect Parliament’s ability to pass legislation, nor limit the words that it can enact into law. In contrast, prorogation of Parliament without lawful excuse may have arisen from the political sphere of the prerogative, but it had a concrete legal effect in that it legally prevented Parliament from legislating. Deepening our understanding of parliamentary sovereignty naturally can include ensuring that Parliament’s functions are legally effective. It is very hard to see how an interpretative obligation qualifies sovereignty.
The only way that this could be seen as limiting Parliament would be if the interpretation of statute was not within the constitutional role of the courts and was instead a parliamentary power. Indeed, it is telling that the Supreme Court here described such provisions as requiring the courts to ‘modify the meaning and effect of legislation’, as if statutes have some independent meaning or effect that is discernible free from the process of judicial interpretation. This understanding would exclude even the understanding of Dicey who argued that:
‘Parliament is supreme legislator, but from the moment Parliament has uttered its will as lawgiver, that will becomes subject to the interpretation put upon it by the judges of the land, and the judges, who are influenced by the feelings of magistrates no less than by the general spirit of the common law, are disposed to construe statutory exceptions to common law principles in a mode which would not commend itself either to a body of officials, or to the Houses of Parliament, if the Houses were called upon to interpret their own enactments … Parliamentary sovereignty has favoured the rule of law … the supremacy of the law of the land both calls forth he exertion of Parliamentary sovereignty, and leads to its being exercised in the spirit of legality’ (The Law of the Constitution, 273)
The only way that s 3 HRA could limit law-making power would be if the Diceyian account of judicial interpretation also did so, and that would only be true if sovereignty (or, if we accept the distinction, law-making power) didn’t mean legislative supremacy, but instead meant that Parliament’s constitutional role includes the exercise of both legislative and judicial powers. But it has never meant that. Parliament does not interpret statutes; courts do.
In construing judicial interpretation of statute as a limitation on Parliament’s law-making powers, the Court has expanded the concept to entail not just its legal effectiveness, free from interference from the prerogative, but also its ‘practical’ effectiveness, free from political constraint. Section 3 of the HRA – again a product of Parliament’s own law-making power – raised ECHR rights to the same status as common law rights by creating a judicial presumption that Parliament does not intend to breach them. Parliament is still perfectly within its legal authority to repeal any part of the HRA or to set out an exception to it if it so chooses. To view this as a qualification of law-making powers is to conflate the power to make law with the power to interpret it.
Furthermore, this presumption that statute does not intend to revoke legal rights is always present when courts interpret law. Regardless of the interpretative methodology adopted, it is never open to a court to simply ignore relevant legislation that touches on the case at hand. The creation of an explicit duty adds greater weight to this presumption, helping to rebut a presumption of implied repeal, but arguably only as a matter of formalising what courts already do. Implied repeal only applies where both statutes, properly understood, conflict. What counts as a proper construction remains the product of judicial interpretation.
It may be tempting to argue, following the Continuity Bill case, that this constitutes a qualification of parliament’s law-making power (but not sovereignty) when the requirement originates from a devolved legislature. But you cannot be limited if you never had the power in the first place. Parliament is the speaker, not the listener. It does not have interpretative powers and there is no default interpretation that courts adopt when discerning the meaning of statutes. They will approach such questions by taking into account all relevant considerations, including devolved legislation or rights-conferring statutes where applicable. If this constitutes a limitation on parliamentary sovereignty, given that Parliament remains free to legislate or amend statute in any devolved area, then any devolved legislation that would affect judicial interpretation of UK legislation in Scotland would be outwith competence. Parliamentary sovereignty has never been this expansive, nor devolution this narrow in scope.
This strained interpretation is compounded by the Court’s second expansion of parliamentary sovereignty with the claim that s 4 of the HRA also qualifies sovereignty: ‘Parliament can itself qualify its own sovereignty, as it did when it conferred on the courts the power to make declarations of incompatibility with rights guaranteed by the ECHR’ . Once more, the only way that this can constitute a limitation on law-making powers is if those powers include or demand the political winds to eternally be favourable. The Court offered three reasons for why declarations of incompatibility qualify parliamentary sovereignty. However, two of these apply only to the Scottish Bills under reference. This leaves one reason for why s 4 HRA would qualify sovereignty: that a finding of incompatibility ‘would impose pressure on Parliament to avoid the opprobrium which such a finding would entail’ . On this view, s 4 is not unconstitutional because Parliament qualified its own sovereignty. Nevertheless, this claim that s 4 qualifies sovereignty is startling. This reasoning clearly manifests a shift to understanding parliamentary sovereignty as including not just the ability of Parliament to legislate in any area that it sees fit, but also the ability of Parliament to do so free from both legal and political impediment.
Does this mean that any judicial finding that might paint Parliament in a bad light or which might result in political pressure on Parliament to change the law would infringe parliamentary sovereignty? This would be absurd. Yet, what else are we to conclude from these comments that pressure to avoid opprobrium limits legislative powers? The Court could have distinguished the provisions in the HRA from the provisions in these Bills, stressing that the HRA did not qualify sovereignty, but these Bills might. But the Court was clear that the HRA limited Parliament’s legislative powers. This was central to its reasoning.
The HRA is not unconstitutional because Parliament is seemingly empowered to qualify its own sovereignty, but the upshot of this judgement is that parliamentary sovereignty is undermined or qualified by judicial findings that impose pressure on Parliament to avoid the opprobrium entailed by them. Parliament is free to direct the courts to do this, thus qualifying its own sovereignty and so the qualification is not unconstitutional. But what about other organs of state? Are the courts themselves free to qualify or undermine sovereignty in this manner by publishing judgments that create similar opprobrium but where the defence that Parliament qualified its own sovereignty is not present? It would be absurd if politically disadvantageous judicial findings qualified sovereignty. But again, what else are we to conclude when the only reason that DOIs don’t is because they arose from an Act of Parliament?
This is made all the more striking when we consider that the court did not need to base its reasoning on this conception of sovereignty. It could have maintained the, admittedly flimsy, distinction between sovereignty and unqualified legislative power introduced in the Continuity Bill judgment. It could have held that both the HRA and the UNCRC Bill qualify legislative power (but not sovereignty) and that this is permitted when the UK Parliament does it, but not when the Scottish Parliament does. Indeed, as Elliott and Kilford note, this is exactly what the Court did with regards to s 28(7) and the analogy with s 3 HRA. Having introduced a gun in the first half of the judgement, it refused to fire it in the second half, preferring instead to ground the ratio of this part of its judgement on the affect these provisions have on parliamentary sovereignty.
The court’s focus on the practical effectiveness of parliamentary sovereignty in Miller II entailed principles which demanded that Parliament remain legally unimpeded in its law-making functions. This was orthodox and correct. Its expansion of sovereignty to include political effectiveness, first in the Continuity Bill case and now here, proves too much. If Parliament is worried that it may face political backlash for acting or failing to act in a given area, then our constitutional order is working. A central tenet of political constitutionalism is that political entities are best held to account through the political process. That method of accountability cannot and should not be construed as a limitation on sovereignty. Parliament’s legal ability to enact legislation is unaffected; the political consequences it faces for action or inaction is not for the Court to concern itself with.
The Supreme Court opining on the political aspects of parliamentary politics would be relatively unimportant if it were not using this expansive definition of sovereignty to ground its adjudication of legal disputes. This strained understanding of what constitutes an interference with the ability of Parliament to make law has concrete practical implications, given that it has used this to radically alter the devolution settlement. What was once seen to be squarely within the realm of politics has begun to be juridified and this is a mistake, the full implications of which have yet to be seen.
My thanks to Chris McCorkindale, Adam Tomkins, Alison Young, and Mike Gordon for helpful comments on previous drafts.
Michael Foran is a Lecturer in Public Law at the University of Strathclyde
(Suggested citation: M. Foran, ‘Parliamentary Sovereignty and the Politics of Law-making’, U.K. Const. L. Blog (18 October 2021) (available at https://ukconstitutionallaw.org/))