Brexit and Parliamentary Sovereignty

TEMPORAL SCOPE: 2016 – 2020

(from the Brexit referendum through the UK’s formal withdrawal from the European Union)

GEOGRAPHIC CONTEXT: United Kingdom (parliamentary democracy with an uncodified constitution; multilevel governance within the EU framework)

Case Trigger & Institutional Conflict #

The 2016 Brexit referendum produced a binding political mandate to leave the European Union without specifying an institutional or procedural pathway for implementation. This created a constitutional shock in the United Kingdom by introducing a direct claim of popular sovereignty into an uncodified constitutional system centered on parliamentary supremacy. The referendum result generated competing authority claims among Parliament, the executive, and the judiciary over who possessed decision-making control. The core institutional problem was how an uncodified constitutional order manages conflicting sources of authority without a clear hierarchy of constitutional rules.

1. Case Overview #

Brexit is analytically significant because it illustrates how institutional systems respond to constitutional stress when foundational principles are contested rather than clearly violated. The case highlights a governance problem in which political actors operated within formal legality but disagreed fundamentally about where ultimate authority resided. Rather than producing institutional collapse, the Brexit process revealed adaptive—but highly strained—patterns of interaction among Parliament, the executive, and the courts. The case demonstrates how parliamentary systems manage authority conflicts under conditions of legal ambiguity and political polarization.

Context & Constraints #

The United Kingdom operates under an uncodified constitution based on statutes, conventions, and judicial interpretation, with parliamentary sovereignty as its core organizing principle. EU membership had already qualified this principle through shared legal authority and supranational judicial oversight. The referendum mechanism, while politically powerful, lacked clear constitutional status relative to Parliament. Political polarization, narrow referendum margins, minority governments, and tight legal deadlines further constrained institutional coordination. These conditions limited actors’ ability to resolve conflicts through established conventions alone.

Key Institutional Actors #

Parliament

• Interests: Preserve legislative supremacy and procedural control
• Resources: Statutory authority, agenda-setting powers, committee oversight
• Constraints: Internal fragmentation, absence of a clear majority strategy

Executive (Prime Minister and Cabinet)

• Interests: Implement Brexit efficiently and maintain negotiating flexibility
• Resources: Control over negotiations, prerogative powers, control of parliamentary timetable
• Constraints: Parliamentary dependence, judicial scrutiny, minority status

Judiciary (UK Supreme Court)

• Interests: Clarify constitutional boundaries and protect legal order
• Resources: Judicial review, constitutional interpretation
• Constraints: Need to avoid overt political decision-making

European Union Institutions

• Interests: Maintain treaty integrity and negotiation coherence
• Resources: Legal frameworks, negotiation leverage
• Constraints: External to UK constitutional hierarchy

Institutional Dynamics & Authority Claims #

The referendum introduced a direct claim of popular sovereignty that the executive interpreted as authorization to act decisively. Parliament resisted this interpretation, asserting that only statutory authority could trigger and shape withdrawal. The executive attempted to centralize authority through prerogative powers and procedural control. Judicial interventions clarified that executive action required parliamentary authorization, reinforcing legal boundaries while intensifying political conflict. Institutional ambiguity allowed all actors to claim legitimacy, producing sustained deadlock rather than decisive resolution.

Theoretical Lens Applied #

Institutionalism (Primary Lens) #

• Why it fits: The case centers on how institutions structure authority, constrain behavior, and adapt under stress.
• Key concepts: formal rules vs. informal conventions, institutional ambiguity, authority allocation.
• Explanatory value: Explains why conflict persisted despite legal continuity and why adaptation occurred without collapse.

Agenda-Setting Theory (Secondary Lens) #

• Why it fits: Control over parliamentary time and sequencing became a central strategic resource.
• Key concepts: agenda control, procedural power, veto points.
• Explanatory value: Clarifies how procedural dominance substituted for substantive consensus.

Outcomes & Consequences #

Immediate effects:

• Judicial clarification of executive limits
• Procedural empowerment of Parliament

Medium-term effects:

• Expansion of judicial constitutional role
• Erosion of traditional conventions governing executive restraint

Unintended consequences:

• Precedents for judicial involvement in constitutional disputes
• Normalization of procedural conflict as a governance strategy

Brexit resulted not in institutional failure but in institutional redefinition under stress.

Analytical Questions #

1. Could Parliament have reduced institutional conflict by clarifying the constitutional status of the referendum earlier?
2. Did judicial intervention stabilize or politicize constitutional governance?
3. How might the same conflict have unfolded under a codified constitution?
4. To what extent did institutional ambiguity enable adaptation versus prolonging deadlock?
5. What does this case suggest about the resilience of parliamentary sovereignty in multilevel governance systems?