A Statutory Instrument (SI) is the principal form of secondary (delegated) legislation in the United Kingdom. Rather than passing a fresh Act of Parliament for every administrative detail, Parliament enacts a "parent" Act that confers power on a minister, department, or other body to make further rules. Those rules are issued as Statutory Instruments and have the force of law.
The framework is set by the Statutory Instruments Act 1946, which standardised numbering, publication, and parliamentary scrutiny. Each SI is given a year and serial number (for example, "SI 2023/123") and published by The National Archives on legislation.gov.uk.
SIs come in several procedural varieties:
- Negative procedure: the instrument becomes law unless either House passes a motion to annul it within 40 sitting days. This is the most common route.
- Affirmative procedure: the instrument requires express approval by resolution of one or both Houses before (or, in some cases, shortly after) it takes effect.
- Made affirmative / "do nothing": variants used for urgent or technical measures.
Common uses include commencing provisions of an Act, setting fees and thresholds, transposing technical regulations, and amending schedules. Statutory Instruments were central to implementing EU law under the European Communities Act 1972 and, after withdrawal, to retaining and amending that body of law under the European Union (Withdrawal) Act 2018, which generated several thousand Brexit-related SIs.
Scrutiny is carried out by the Joint Committee on Statutory Instruments (JCSI) for technical defects, and by the Secondary Legislation Scrutiny Committee in the Lords for policy merits. Courts can review SIs for ultra vires — that is, whether the minister exceeded the powers granted by the parent Act — as confirmed in cases such as R (Public Law Project) v Lord Chancellor [2016] UKSC 39.
Devolved legislatures in Scotland, Wales, and Northern Ireland produce their own equivalents, such as Scottish Statutory Instruments (SSIs).
Example
In 2020, the UK government used Statutory Instruments such as the Health Protection (Coronavirus, Restrictions) (England) Regulations 2020 to impose lockdown rules under powers in the Public Health (Control of Disease) Act 1984.
Frequently asked questions
An Act is primary legislation passed by both Houses and given Royal Assent. A Statutory Instrument is secondary legislation made by a minister under powers an Act has already conferred, with much lighter parliamentary scrutiny.
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