Author: Amarpreet Kaur, University of Edinburgh
To the Point
In constitutional democracies, the most serious threats to legality rarely arise through overt defiance of the law. Instead, they emerge when executive authorities act assertively within legally ambiguous spaces, often justified by political urgency, national interest, or democratic mandate. In the United Kingdom, the absence of a codified constitution and the traditional reliance on constitutional conventions have historically afforded the executive considerable discretion in governance. While political accountability has long been regarded as the primary constraint on executive action, modern public law increasingly recognises that political mechanisms alone are insufficient where constitutional fundamentals are at stake.
The Brexit process exposed these structural vulnerabilities with unusual clarity. Executive reliance on prerogative powers, attempts to limit parliamentary scrutiny, and resistance to judicial oversight created a constitutional environment in which the boundaries of lawful authority were actively contested. These developments did not merely reflect political disagreement. They raised profound legal questions about the distribution of power within the UK constitution and the mechanisms through which that power is controlled.
This article argues that judicial control of executive power in the United Kingdom is not an intrusion into politics but a constitutional necessity for preserving the rule of law. Through an in depth analysis of key Supreme Court decisions, particularly those arising during the Brexit era, it demonstrates that courts play an essential role in maintaining legal accountability when political pressures threaten to overwhelm constitutional safeguards. Far from undermining democratic legitimacy, judicial review functions as a stabilising force that preserves the conditions under which democratic governance can operate lawfully.
Use of Legal Jargon
The analysis engages foundational doctrines of UK constitutional and administrative law. Executive authority in the United Kingdom derives in part from prerogative powers, which are residual powers historically exercised by the Crown and now deployed by ministers. Although once regarded as largely immune from judicial scrutiny, prerogative powers are now subject to review where their exercise affects legal rights or constitutional principles.
Justiciability refers to whether an issue is suitable for judicial determination. Contemporary UK jurisprudence increasingly rejects the notion that political sensitivity alone renders a matter non justiciable. Instead, courts ask whether there exist legal standards capable of guiding judicial assessment. Where constitutional principles such as parliamentary accountability or the rule of law are implicated, courts have been willing to assert jurisdiction.
Central to this framework is the rule of law, which requires that all public power be exercised according to law and that legal limits on authority be enforceable in practice. The principle of legality reinforces this requirement by holding that fundamental constitutional change demands clear and explicit statutory authorisation. Closely linked is the constitutional principle of access to justice, without which legal rights become merely theoretical.
Although the United Kingdom does not adhere to a rigid separation of powers, its constitutional order depends upon an institutional balance. Parliament provides political accountability, while courts ensure legal accountability. Judicial review operates as the mechanism through which this balance is maintained, particularly when executive action threatens to disrupt it.
The Proof
Brexit as a Constitutional Stress Test
Brexit constituted the most significant constitutional stress test in modern UK history. The process generated sustained political urgency, institutional conflict, and uncertainty regarding the scope of executive authority. Long standing constitutional conventions, which had previously regulated the relationship between government, Parliament, and courts, proved inadequate when confronted with sustained political polarisation.
The executive increasingly relied on prerogative powers to manage withdrawal from the European Union, raising fundamental questions about the limits of such authority. Parliamentary scrutiny was periodically constrained, and political rhetoric framed judicial intervention as an obstacle to democratic will. In this context, litigation did not represent judicial opportunism. Rather, it reflected the courts responding to a constitutional vacuum in which legal boundaries required clarification. The Brexit litigation therefore exposed the limitations of constitutional conventions as effective constraints on executive power when political actors are willing to disregard them, highlighting the need for enforceable legal standards rather than reliance on good faith.
Miller v Secretary of State for Exiting the European Union (No 1)
In Miller (No 1), the Supreme Court addressed whether the government could trigger Article 50 of the Treaty on European Union using prerogative powers alone. The Court held that it could not. Withdrawal from the European Union would alter domestic law and extinguish statutory rights created by Parliament. Such constitutional change required parliamentary authorisation.
The significance of the decision lies not merely in its outcome but in its constitutional reasoning. The Court reaffirmed the foundational principle that prerogative powers cannot be used to override legislation. Parliamentary sovereignty, properly understood, requires that changes to domestic law flow from Parliament rather than unilateral executive action.
Importantly, the Court resisted framing its analysis in political terms. It neither endorsed nor criticised Brexit as a policy choice. Instead, it focused on constitutional structure and legal authority. This approach demonstrates how judicial control of executive power can be exercised without encroaching upon political decision making.
Miller v Prime Minister and Cherry v Advocate General (No 2)
The constitutional stakes of judicial oversight were further clarified in Miller (No 2). The Supreme Court unanimously held that the Prime Minister’s advice to prorogue Parliament was justiciable and unlawful where it had the effect of frustrating Parliament’s constitutional functions without reasonable justification.
This judgment is frequently criticised as an instance of judicial overreach. Critics argue that prorogation is a political matter and that judicial intervention undermines democratic accountability. However, such criticism overlooks the Court’s method. The Court did not assess political motive or policy wisdom. It articulated a legal standard focused on constitutional effect and justification.
The declaration that the prorogation was null and of no legal effect is particularly significant. It affirms that unlawful executive action does not acquire legitimacy through political context or urgency. Without such judicial enforcement, the executive could suspend parliamentary scrutiny at moments of political inconvenience, fundamentally weakening responsible government.
R (UNISON) v Lord Chancellor and Structural Accountability
Judicial control of executive power extends beyond headline constitutional crises. In UNISON, the Supreme Court struck down employment tribunal fees imposed by the executive. The Court held that access to justice is a constitutional principle inherent in the rule of law and that statutory rights are rendered ineffective if individuals cannot realistically enforce them.
This case illustrates a more subtle form of executive overreach. Rather than directly excluding judicial scrutiny, the executive imposed financial barriers that discouraged legal claims. The Court’s intervention reflects an understanding of constitutional accountability that extends beyond formal legality to practical effectiveness.
UNISON demonstrates that judicial review plays a critical role in preserving democratic accountability indirectly. By ensuring that legal remedies remain accessible, courts maintain the capacity of individuals to challenge unlawful exercises of power.
R (Evans) v Attorney General and Executive Resistance
In Evans, the Supreme Court considered the scope of an executive veto under the Freedom of Information Act 2000. The Attorney General sought to override a judicial decision requiring disclosure of correspondence involving the Prince of Wales. The Court held that such an override was incompatible with constitutional principles relating to the separation of powers and the finality of judicial decisions.
The case is significant because it confronts a recurring executive impulse to reserve the final word on matters of legality. The Court’s restrictive interpretation of the veto reflects judicial insistence that political authority does not extend to nullifying judicial determinations absent clear statutory language.
Evans reinforces the principle that judicial control of executive power operates not only during constitutional emergencies but also within routine mechanisms of accountability such as transparency and information access.
Responding to the Politicisation Critique
A persistent critique of judicial intervention in politically sensitive cases is that courts risk becoming politicised and undermining democratic legitimacy. This concern is not without force. Courts derive legitimacy from legal reasoning rather than electoral mandate, and excessive intervention could distort constitutional balance. However, comparative constitutional practice demonstrates that judicial review of executive action is widely accepted as a safeguard against constitutional erosion in democratic systems, particularly where political accountability mechanisms prove insufficient.
The alternative, however, is more troubling. Where executive power expands into legally ambiguous spaces without enforceable limits, political accountability alone proves insufficient. Elections operate retrospectively and cannot remedy immediate constitutional harm. Judicial review, by contrast, provides timely and principled enforcement of legal boundaries.
The legitimacy of judicial control therefore depends on disciplined methodology. Courts must articulate clear legal standards, ground their reasoning in constitutional principle, and avoid substituting political preference for legal judgment. The Brexit era jurisprudence demonstrates that such discipline is achievable even under intense political pressure.
Abstract
This article critically examines judicial control of executive power in the United Kingdom through the lens of Brexit era constitutional litigation. It argues that Supreme Court intervention in politically sensitive cases reflects principled enforcement of constitutional fundamentals rather than judicial politicisation. Through analysis of Miller (No 1), Miller (No 2), UNISON, and Evans, the article demonstrates that judicial review operates as a necessary legal mechanism for preserving parliamentary accountability, access to justice, and the rule of law during periods of political instability.
Case Laws
1. Miller v Secretary of State for Exiting the European Union (No 1) [2017] UKSC 5
In Miller (No 1), the UK Supreme Court held that the government could not trigger Article 50 of the Treaty on European Union through the use of prerogative powers alone. The Court reasoned that withdrawal from the European Union would result in changes to domestic law and the removal of statutory rights created by Parliament, which required explicit parliamentary authorisation. This decision reaffirmed the constitutional principle that prerogative powers cannot be exercised in a manner that overrides or frustrates legislation enacted by Parliament. The case established a crucial limit on executive authority during politically significant decision making.
2. Miller v Prime Minister; Cherry v Advocate General for Scotland (No 2) [2019] UKSC 41
In Miller (No 2), the Supreme Court examined the lawfulness of the Prime Minister’s advice to prorogue Parliament during the Brexit process. The Court held that the prorogation was justiciable and unlawful where it had the effect of frustrating Parliament’s ability to perform its constitutional functions without reasonable justification. By declaring the prorogation null and of no legal effect, the Court reinforced the principle that executive power remains subject to legal limits even in politically sensitive contexts. This case represents a landmark affirmation of judicial control over executive action in defence of parliamentary accountability.
3. R (UNISON) v Lord Chancellor [2017] UKSC 51
The decision in UNISON concerned the legality of employment tribunal fees introduced by the executive. The Supreme Court held that the fees were unlawful as they impeded access to justice, which the Court recognised as a fundamental constitutional principle inherent in the rule of law. The judgment emphasised that statutory rights are rendered ineffective if individuals cannot realistically enforce them through legal processes. This case illustrates how judicial review can restrain executive measures that indirectly undermine constitutional accountability.
4. R (Evans) v Attorney General [2015] UKSC 21
In Evans, the Supreme Court considered whether the Attorney General could lawfully exercise a statutory veto to override a judicial decision requiring disclosure of information under the Freedom of Information Act 2000. The Court held that such an override was incompatible with constitutional principles relating to the separation of powers and the finality of judicial decisions. The ruling limited executive discretion to disregard judicial determinations without clear statutory authority. This case underscores the judiciary’s role in preventing executive dominance over legal accountability mechanisms.
Conclusion
The Brexit era exposed constitutional tensions that had long existed beneath the surface of the United Kingdom’s political system. Executive reliance on prerogative powers, attempts to limit scrutiny, and resistance to judicial oversight revealed the fragility of constitutional conventions when confronted with sustained political urgency.
Judicial control of executive power did not emerge as an act of political interference but as a response to constitutional necessity. Through careful reasoning grounded in the rule of law, parliamentary accountability, and access to justice, the courts clarified the legal limits of executive authority. These decisions affirm that democratic legitimacy depends not only on electoral mandate but also on adherence to enforceable legal constraints. While Parliament remains the central forum for political accountability, courts are uniquely positioned to provide immediate and enforceable limits on unlawful executive action.
The constitutional lesson of the Brexit litigation is therefore enduring. In moments of crisis, the rule of law is tested most severely. Judicial review functions as the mechanism through which constitutional order is preserved when political processes alone prove insufficient.
FAQS
Is judicial review incompatible with democratic decision making?
Judicial review is not incompatible with democratic decision making. It enforces the legal limits within which democratic institutions operate and protects Parliament’s constitutional role. Rather than displacing political decision making, judicial review ensures that democratic authority is exercised in accordance with constitutional and legal principles.
Did Brexit politicise the judiciary?
Brexit exposed constitutional ambiguities that required legal clarification, particularly concerning executive power and parliamentary accountability. The courts responded by applying established legal principles rather than political preferences, intervening only where constitutional fundamentals were threatened.
Why are prerogative powers subject to judicial scrutiny?
Prerogative powers affect legal rights and constitutional principles, including parliamentary sovereignty and the rule of law. Where their exercise has legal consequences, courts are required to ensure that such powers are exercised lawfully and within constitutional limits.
Why is access to justice constitutionally significant?
Access to justice ensures that legal rights can be enforced in practice rather than remaining purely theoretical. Without meaningful access to courts and tribunals, the rule of law becomes ineffective and statutory protections lose their practical value.
What is the broader constitutional significance of the Brexit cases?
The Brexit cases confirm that executive power in the United Kingdom remains subject to legal accountability, even during periods of intense political pressure. They demonstrate that courts play a crucial role in preserving constitutional order when political mechanisms alone are insufficient.
