Separation of powers & constitutional conventions

LS.05 — Separation of Powers & Constitutional Conventions

Separation of powers

The UK has a partial separation, not a strict one. Three branches:

• Legislature (Parliament) — makes law
• Executive (Government/Crown) — applies/implements law
• Judiciary (courts) — interprets and applies law

Overlap is built in: ministers (executive) sit in and are drawn from Parliament (fusion). The Constitutional Reform Act 2005 sharpened the separation by:

• Creating the UK Supreme Court (operational 2009), removing the top court from the House of Lords.
• Reforming the Lord Chancellor's role (no longer head of the judiciary; s.3 places a statutory duty to uphold judicial independence).
• Creating the Judicial Appointments Commission (merit-based, removing patronage).

Judicial independence is reinforced by security of tenure (senior judges hold office "during good behaviour", removable only on an address by both Houses — Senior Courts Act 1981 s.11) and salaries charged on the Consolidated Fund.

Constitutional conventions

Definition (Dicey): non-legal rules of constitutional practice, regarded as binding, but not legally enforceable by the courts.

Jennings' test for whether a convention exists:

1. Precedents — is there a practice?
2. Belief — did the actors feel bound by the rule?
3. Reason — is there a good constitutional reason for it?

Key conventions:

• The monarch grants Royal Assent on advice and does not refuse it.
• The monarch appoints as PM the person able to command the confidence of the Commons.
• Collective and individual ministerial responsibility to Parliament.
• The Sewel convention — Westminster does not normally legislate on devolved matters without the devolved legislature's consent.

Conventions vs law — the critical traps

• Courts recognise conventions but will not enforce them. Attorney-General v Jonathan Cape (1976) — Cabinet confidentiality is a convention; enforced only via the equitable confidence jurisdiction, not as a convention per se.
• R (Miller) v Secretary of State (No 1) [2017] — the Sewel convention is not legally enforceable even though codified in statutory words (Scotland Act 1998 s.28(8) "will not normally"); "normally" plus convention = political, not justiciable.
• Miller No 2 [2019] (prorogation) — courts WILL enforce legal limits on prerogative power; that case turned on legality, not breach of a convention.

Distinctions to nail

• Convention breached → political consequence, never a remedy in court.
• Law breached → court remedy available.
• The rule of law (Dicey: no punishment except for breach of law, equality before law, rights from common law) is a constitutional principle, expressly recognised in CRA 2005 s.1.