A writ of prohibition is a court order stopping a lower court, tribunal or public body from continuing proceedings because it is acting outside, or in excess, of its lawful jurisdiction. In modern practice across England and Wales, Northern Ireland and Ireland, this remedy survives as a form of judicial review, usually called an order of prohibition rather than a traditional “writ”.It is typically sought where a decision‑maker proposes to hear a case it has no power to determine, applies the wrong legal test so fundamentally as to exceed its powers, or ignores mandatory procedural requirements. It is generally prospective, restraining further steps rather than quashing a decision already made (for which certiorari/quashing orders are used), though the remedies may overlap.The principles are largely case‑law based, reflecting the historic supervisory jurisdiction of the higher courts (High Court; Court of Session in Scotland). In Scotland, prohibition is part of the Court of Session’s nobile officium and judicial review jurisdiction, serving a similar function of preventing unlawful excess of jurisdiction.Practitioners use prohibition to protect clients from ultra vires regulatory or disciplinary proceedings, criminal prosecutions before the wrong court, and other unlawful exercises of public power.