A Tale of Two Doctrines: Revaluating Bifurcation in Substantive Review before the Supreme Court

Abstract

Debates over bifurcation in substantive review persist; should Wednesbury review subsist alongside a proportionality-based model, or should substantive review depend solely upon proportionality? Drawing on an analysis of UK Supreme Court decisions between 2014 and 2018, we argue that the academic debate and much recent jurisprudence misconstrue substantive review. Both proportionality and Wednesbury display their own internal (“intra-doctrinal”) bifurcation between judge-centric and deferential approaches. Although proportionality’s application under the Human Rights Act 1998 has generated culture of justification in rights cases, fixation on the test’s rights/aims balancing aspects has embroiled judges in value adjudication. Faced with preferring either legal or policy aims, the Court has at times fluctuated between strong and weak oversight. Traditional Wednesbury review, while methodologically distinct, can also swing between highly deferential reasonableness review and more robust review drawing, for example, on statutory purpose. Substantive review thus currently risks contradictory pathologies; deploying legal trumps to preclude political decision making and permitting clear policy failures. These pathologies stem from UK public law’s inadequate engagement with substantive decision making. We therefore re-evaluate functionalist constitutionalism, advancing an active functionalist model which urges public lawyers, outwith instances of illegality, to maximise institutional effectiveness. By prioritising legitimacy as an organising principle for judicial review, this approach sustains political decision making within the bounds of a liberal democratic order.