Does Miller (No 1) threaten dualism?
The UK traditionally follows a 'dualist' approach: treaties (international law) are made by the executive under prerogative and have no direct effect in domestic law absent implementing legislation. Miller (No 1) reinforces this: triggering Article 50 was an exercise of prerogative in the international sphere, but because it would change domestic law (by removing statutory rights), parliamentary authorisation was required.
Yet some scholars (Finnis, 2016) argue the decision risks collapsing dualism. If every treaty notification that has domestic consequences requires legislation, executives lose flexibility in international relations. Proponents (Elliott, 2017; Young, 2017) respond that Miller does not require parliamentary authorisation for all treaty acts—only those that would alter or remove rights arising under domestic statute. The case is thus consistent with dualism, properly understood.
Constitutional statutes and prerogative
Miller (No 1) cites Thoburn and treats the ECA 1972 as a 'constitutional statute' of special importance. Does this mean prerogative is more limited when it comes to constitutional statutes? Laws LJ's obiter in Thoburn (at [62]) suggested such statutes could not be impliedly repealed; Miller extends this logic to prerogative displacement: constitutional statutes cannot be displaced by prerogative at all.
Craig (2016) and Elliott (2017) argue this reflects a hierarchy of norms emerging in UK constitutional law. Critics such as Ekins (2017) warn that judicial recognition of 'constitutional statutes' undermines the equality of all statutes and parliamentary sovereignty.
Was Miller (No 2) justiciable?
The most polarised academic debate concerns Miller (No 2). Finnis and Ekins argue the Court exceeded its proper role: decisions about prorogation are inherently political, involve assessment of government motive and parliamentary time management, and should be resolved by political processes (election, confidence votes), not judicial review.
Elliott, King, and Young defend the decision: the courts are guardians of constitutional principle, and where executive action threatens Parliament's ability to function, legal limits exist and courts must enforce them. On this view, Miller (No 2) is an application of the rule of law (Week 4, Bingham's principles, especially legal limits on executive power).
Tomkins (2020) occupies a middle position: the outcome was correct (the prorogation was constitutionally improper) but the courts should not have intervened—conventions and politics should have resolved the matter.
Unwritten constitutionalism and common-law rights
Miller (No 2) cites no statute. The legal limits it enforces derive from constitutional principle. This aligns with a tradition of common-law constitutionalism (Allan, Elliot, Laws LJ in Thoburn) that regards the rule of law and fundamental rights as inherent constraints on all public power, including Parliament.
This conflicts with orthodox Diceyan sovereignty, which treats Parliament as legally unlimited. Supporters of common-law constitutionalism argue Dicey's account was always incomplete: even in Dicey's time, courts asserted interpretive principles (e.g., Entick v Carrington (1765)) and recognised limits on arbitrariness. Miller (No 2) is consistent with this tradition.
Critics regard this as judicial activism: unelected judges substituting their view of the constitution for that of elected politicians. The debate mirrors the Jackson controversy (Week 3) about whether courts could invalidate legislation that violated fundamental principles.
Impact on the separation of powers
Miller (No 2) is explicitly grounded in separation of powers: Parliament's role is to legislate, scrutinise, and hold the executive accountable; prorogation frustrated this. The Court thereby enforced a structural constitutional principle.
Some argue this extends the separation of powers beyond its traditional scope. Historically, the UK does not have a rigid separation: the executive sits in Parliament, exercises legislative initiative, and controls the parliamentary timetable. Critics (Ekins, Tomkins) contend the Court imposed an idealised model of separation foreign to Westminster practice.
Parliamentary sovereignty and the Courts
Both Miller cases assert that courts exist to uphold parliamentary sovereignty. In Miller (No 1), the Court prevented the executive from bypassing Parliament. In Miller (No 2), it prevented the executive from silencing Parliament. Yet in both cases, the courts told Parliament and the executive what they could or could not do.
This raises the paradox: can courts enforce sovereignty without themselves becoming sovereign? Goldsworthy (2016) argues judicial enforcement of sovereignty risks judicial supremacy. Allan (2017) responds that sovereignty is a rule of the common law, and courts are its authoritative interpreters. The debate is unlikely to be resolved; it reflects different conceptions of the constitution.