Parliamentary sovereignty & rule of law

LS.04 — Parliamentary Sovereignty & the Rule of Law

Parliamentary sovereignty (Dicey)

The orthodox doctrine has three limbs:

• Parliament can make or unmake any law on any subject.
• No Parliament can bind its successors (a later Act overrides an earlier one).
• No body can override or set aside an Act of Parliament — courts apply, they do not strike down primary legislation.

Implied repeal: where two Acts conflict, the later impliedly repeals the earlier (Vauxhall Estates; Ellen Street Estates).

"Constitutional statutes" exception: statutes of constitutional importance (e.g. Magna Carta, Bill of Rights 1689, ECA 1972, HRA 1998, Scotland Act, devolution Acts) are not subject to implied repeal — they can only be repealed by express words (Thoburn v Sunderland (the "Metric Martyrs" case); HS2).

Courts and statute: courts cannot invalidate an Act. Under HRA 1998 s.4 the senior courts may issue a declaration of incompatibility — this does not strike down or affect the validity of the legislation; it leaves it in force and signals to Parliament.

Rule of law

A constitutional principle, expressly recognised in s.1 Constitutional Reform Act 2005. Dicey's core: (1) no punishment except for a breach of law established in the ordinary courts; (2) equality before the law; (3) rights derive from ordinary law/case law. Raz's formal version stresses clarity, prospectivity, accessibility, and access to independent courts. Underpins judicial review and the principle of legality (R v SSHD ex p Simms: fundamental rights cannot be overridden by general/ambiguous words).

EU law / assimilated law (current to 2026)

• REUL Act 2023 renamed retained EU law as "assimilated law" and ended supremacy from 1 January 2024.
• Trap: REUL Act 2023 s.6 (new departure test + lower-court reference route) never came into force (commencement revoked, SI 2024/976). The EUWA 2018 s.6 framework still governs: only the Court of Appeal and Supreme Court may depart from assimilated case law (on the own-precedent basis); lower courts and tribunals remain bound.

Common traps

• A declaration of incompatibility does not invalidate the statute.
• Courts cannot strike down primary legislation; they can quash secondary legislation/executive action.
• Constitutional statutes = express repeal only, not implied.
• Don't cite REUL s.6 as live law — it isn't.