The United Kingdom has three legal systems. English law, which applies in England and Wales, and Northern Ireland law, which applies in Northern Ireland, are based on common-law principles. Scots law, which applies in Scotland, is a pluralistic system based on civil-law principles, with common law elements dating back to the High Middle Ages. The Treaty of Union, put into effect by the Acts of Union in 1707, guaranteed the continued existence of a separate law system for Scotland. The Acts of Union between Great Britain and Ireland in 1800 contained no equivalent provision but preserved the principle of separate courts to be held in Ireland, now Northern Ireland.
The Appellate Committee of the House of Lords (usually just referred to, as "The House of Lords") is the highest court in the land for all criminal and civil cases in England and Wales and Northern Ireland, and for all civil cases in Scots law. Recent constitutional changes will see the powers of the House of Lords transfer to a new Supreme Court of the United Kingdom.
In England and Wales, the court system is headed by the Supreme Court of England and Wales, consisting of the Court of Appeal, the High Court of Justice (for civil cases) and the Crown Court (for criminal cases). The Courts of Northern Ireland follow the same pattern. In Scotland the chief courts are the Court of Session, for civil cases, and the High Court of Justiciary, for criminal cases, while the sheriff court is the Scottish equivalent of the county court.
The Judicial Committee of the Privy Council is the highest court of appeal for several independent Commonwealth countries, the British overseas territories, and the British Crown dependencies. There are also immigration courts with UK-wide jurisdiction