A bylaw (UK: byelaw; Ireland: bye-law) is a rule made by a local authority or other public, chartered or regulatory body, under statutory powers, to regulate behaviour in a defined place or system (for example parks, highways or railways). It is subordinate legislation: the enabling Act confers the power, sets procedure (typically consultation and publication) and limits content and penalties.Across England & Wales and Scotland, many byelaws require confirmation by a Secretary of State or the Scottish Ministers (with an alternative approval route for some English local authority byelaws). In Northern Ireland, council byelaws are typically confirmed by a Department. In Ireland, local authorities and some statutory bodies make bye-laws under the Local Government Act 2001 and sectoral statutes; ministerial confirmation is generally not required.Key legal features: a bylaw must be intra vires, reasonable, certain and not repugnant to general law; it operates only within the maker’s jurisdiction. Breach is ordinarily a summary offence enforceable in the magistrates’ court (E&W, NI), sheriff court (Scotland) or District Court (Ireland), with fines or fixed payments where authorised. Byelaws are challengeable by judicial review. Do not confuse with US‑style corporate “bylaws”; UK companies use articles of association.