The United Kingdom is the source of the common law tradition: law built case by case in royal courts, carried around the world by empire, and still developing in London today. Yet the UK itself is unusual within its own family — it has no single written constitution, and its courts cannot strike down an Act of Parliament.
It is also not one legal system but three. England and Wales share a common law jurisdiction; Northern Ireland has its own, closely related; and Scotland runs a mixed system with civil-law roots, keeping its own courts and — in criminal matters — its own final court of appeal.
The elected House of Commons decides who governs and has the final say on legislation. The House of Lords — mostly appointed life peers — revises and delays but ultimately defers. Together they are sovereign: no UK court can strike down an Act of Parliament.
The King is head of state, acting almost entirely on the advice of ministers. The government is formed by whoever commands the confidence of the Commons — the model Canada, Australia and New Zealand all inherited.
Since 1998, devolved legislatures make law on health, education, justice and more. Unlike a federation, devolution is a grant from Westminster, not a constitutional division — Parliament could, in law, take the powers back.
England and Wales, Scotland, and Northern Ireland each have their own courts and legal professions. Scots private law draws on Roman civil law — a mixed system inside the common law's home state.
The final court of appeal for the whole UK in civil matters, and for England, Wales and Northern Ireland in criminal matters — Scottish criminal appeals end at Scotland's own High Court of Justiciary. It replaced the Appellate Committee of the House of Lords in 2009.
This pyramid is the English and Welsh one. Northern Ireland mirrors it; Scotland has its own structure — sheriff courts, the Court of Session for civil cases, and the High Court of Justiciary for crime.
Courts interpret statutes but cannot invalidate them. Under the Human Rights Act they can declare a statute incompatible with human rights — a formal signal that leaves the fix to Parliament, which usually, but not always, responds.
Decisions of the Supreme Court bind every other court; the Court of Appeal binds the courts below and, generally, itself. Since a 1966 Practice Statement the top court may depart from its own past decisions — sparingly.
Judges are appointed from the practising profession through an independent Judicial Appointments Commission, and hold office during good behaviour — a security of tenure dating to the Act of Settlement 1701.
Lawyers divide into solicitors, who advise clients and conduct litigation, and barristers, who specialise in courtroom advocacy — a division most of the common law world (including Canada) merged, but the UK largely kept.
Juries decide serious criminal trials in the Crown Court, but have almost vanished from civil cases — defamation was the last redoubt, and even that ended for most claims in 2013.
Canada's inheritance runs straight through London: English common law arrived with colonial courts, and until 1949 Canadian appeals ended at the Judicial Committee of the Privy Council. UK decisions are no longer binding in Canada, but they remain persuasive — Canadian courts still cite the UK Supreme Court regularly.