There are two main types of legislation: primary and secondary (or delegated). Secondary legislation is made under the authority of a piece of primary legislation. Examples of primary legislation are: Acts of Parliament; Acts of the pre-UK parliament (acts by independent parliaments of the separate countries prior to unification in 1801); Acts of the devolved parliaments; Church of England Measures; and Prerogative Instruments. Examples of secondary legislation are: statutory instruments made under Acts of Parliament (orders, rules, and regulations); Scottish and Welsh statutory instruments; statutory rules of Northern Ireland; Church instruments; and bye-laws.[i]
Although secondary legislation is often referred to as a statutory instrument, primary legislation may also be referred to as statutes. This distinction is important for purposes of understanding the law in the UK, and it is also important in the Bluebook as there are different citation forms for “Statutes” meaning primary legislation and “Regulations” meaning secondary legislation.
[i] The National Archives, Guide to Revised Legislation on Legislation.Gov.UK, Legislation.Gov.UK (Jan. 2012), http://www.legislation.gov.uk/pdfs/GuideToRevisedLegislation_Jan_2012.pdf.