Primary authority describes legal sources that have binding force or authoritative status in legal research and argument, as opposed to persuasive or secondary materials. In UK and Irish practice, it is a descriptive term rather than a defined statutory concept, but is widely used in litigation, advisory work and academic commentary.Primary authority typically includes: legislation (Acts of Parliament/Oireachtas, devolved legislation, statutory instruments), constitutional texts, EU law still retained or applicable, and case law from courts whose decisions are binding on the forum court (for example, Supreme Court, Court of Appeal, High Court, Court of Session, Court of Appeal in Northern Ireland, Irish Supreme Court and Court of Appeal).Lawyers rely on primary authority to establish the ratio decidendi, interpret statutes, and demonstrate the current state of the law in submissions, opinions and legal drafting. Usage of the term is broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland, though the hierarchy of courts and specific constitutional sources differ by jurisdiction. Primary authority is contrasted with secondary sources, such as textbooks, articles, Practice Directions and non‑binding guidance.