Devolution and the Sewel Convention

Devolution preserves Westminster's legal sovereignty while creating political constraints through the Sewel Convention. Section 28(7) Scotland Act 1998 maintains that devolution 'does not affect the power of the Parliament of the United Kingdom to make laws for Scotland.' Yet section 28(8), inserted in 2016, 'recognises' that Westminster 'will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament.' This creates a constitutional paradox: Westminster retains unlimited legal power but operates under binding political constraint. The Supreme Court in Miller (No 1) held the Convention non-justiciable, treating it as political rather than legal. The rationale is that conventions operate through political accountability, not judicial enforcement—courts police legality, not political practice.

R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5: Held the Sewel Convention non-justiciable despite statutory codification—'the policing of its scope and manner of operation does not lie within the constitutional remit of the judiciary.' Establishes that statutory recognition of a convention does not transform it into law.

AXA General Insurance Ltd v Lord Advocate [2011] UKSC 46: Confirmed devolved legislation is subject to judicial review for competence and potentially for compatibility with fundamental common law principles. Demonstrates that devolved Acts, though primary in effect, remain subordinate constitutionally.

Imperial Tobacco Ltd v Lord Advocate [2012] UKSC 61: Applied purposive approach to devolved competence—legislation must 'relate to' reserved matters, not merely have consequential effects. Shows courts interpret competence generously to protect devolution.

Reference re UK Withdrawal (Legal Continuity) (Scotland) Bill [2018] UKSC 64: Struck down provisions exceeding Scottish Parliament's competence. Illustrates active judicial policing of legislative competence boundaries.

Robinson v Secretary of State for Northern Ireland [2002] UKHL 32: Required generous, purposive interpretation of devolution statutes given their constitutional importance. The constitutional context shapes statutory construction.

Courts assess devolved legislation through section 29 Scotland Act 1998 (and equivalents): Is it within competence? This requires checking whether provisions (1) relate to reserved matters (Schedule 5), (2) breach Convention rights, or (3) modify protected enactments impermissibly. The 'relate to' test is purposive—examining the provision's essential purpose, not incidental effects (Imperial Tobacco). For the Sewel Convention, the process is purely political: Westminster seeks consent via Legislative Consent Motion (LCM); if refused, Parliament decides whether circumstances are sufficiently exceptional to legislate anyway under the 'normally' exception. Brexit demonstrated this: Scotland and Wales withheld consent for withdrawal legislation; Westminster proceeded, citing exceptional constitutional circumstances. Courts will not review whether the 'normally' threshold is met—this remains a political judgment.

Conflating legal and political: Stating Westminster 'cannot' legislate on devolved matters. Westminster legally can (s.28(7))—the constraint is political only. Treating devolved Acts as unreviewable: ASPs are primary in effect but subordinate constitutionally—courts can strike them down for exceeding competence. Misreading Miller: The Court did not say the Convention doesn't exist, but that it's non-justiciable. Ignoring 'normally': The Convention explicitly permits exceptions—Brexit tested this escape clause. Claiming entrenchment: Constitutional statutes cannot be impliedly repealed (Thoburn) but can be expressly repealed—devolution isn't legally entrenched.