Why legislation binds, how Acts, statutory instruments and guidance fit together, and the limits of what the written text can tell you.
Why does any of this matter if you are not a lawyer? A legal maxim the courts still cite gives the honest answer:
Ignorantia juris non excusat (Ignorance of the law is no excuse)
A person cannot escape criminal or civil liability merely by showing they did not know their conduct was unlawful — in contrast to a mistake of fact, which may sometimes excuse. This harsh-sounding rule is only workable because the law is, in principle, publicly accessible: legislation is formally published (historically in the London, Edinburgh and Belfast Gazettes, now consolidated on legislation.gov.uk), so that a person is taken to have had the means to know it even if they did not in fact consult it. The maxim is regularly invoked by the state to reject a defence based on unfamiliarity with a statute or regulation. Its harshness has, however, driven arguments — not always successful — that particular laws must be sufficiently accessible and foreseeable in their effect to be enforced consistently with the rule of law and with Article 7 ECHR, especially where a criminal offence is defined in technical subordinate legislation few could reasonably be expected to have found.
— Halsbury's Laws of England (5th edn), vol 47, 'Statutes'
The maxim's point is uncomfortable but useful: not knowing about a rule does not make it go away. These pages exist so the rules, and the places they live, are easier to find.
Most of the law that affects everyday life arrives in layers. Parliament debates and passes an Act, which sets the framework. An Act frequently hands a minister the power to fill in the detail later, by making regulations known as statutory instruments. Regulators and government departments then publish guidance about how they apply both.
UK Primary and Secondary legislation: 'Primary legislation' is the term used to describe the main laws passed by the legislative bodies of the UK e.g. Acts of the UK Parliament, Scottish Parliament, Welsh Parliament and Northern Ireland Assembly. It also includes Acts passed by historical parliaments, other primary legislation for Northern Ireland and Church of England Measures (legislation for the established church in England passed by the General Synod of the Church of England ). These types of legislation are sometimes referred to as 'statutes' and the term 'the statute book' refers to the whole of the statute law currently in force.
— Understanding Legislation (legislation.gov.uk): How legislation works — read in full ↗
This is worth remembering when you are hunting for an answer: the specific rule is often not in the Act at all, but in a statutory instrument made under it. When an Act seems silent, the regulations made under it are usually the next place to look.
Legislation is one part of the law, not the whole of it. Courts decide what its words mean in real disputes, and public bodies apply it day to day. Reading an Act on its own does not always show how it works in practice.
Law changes, and published text takes time to catch up. legislation.gov.uk, the official source this service draws on, describes its own editorial timescales:
Revising legislation on legislation.gov.uk involves amending the text of the legislation where appropriate and adding annotations containing information about effects on legislation, or other editorial information. We aim to present the revised text of legislation clearly and accurately without gloss or comment, giving authority for changes to the text, and recording any other effects that make some difference to the meaning, scope or application of the legislation. But otherwise, we aim to let the legislation speak for itself precisely as the legislature has framed it.
— Understanding Legislation (legislation.gov.uk): Our editorial practice and timescales — read in full ↗
Our plain English is not the law. When Ask The Beagle explains a provision in ordinary words, that explanation is a guide to the cited source, never a replacement for it. If it matters, read the source the citation points to.