The United States took the common law it inherited as thirteen colonies and re-founded it on a written constitution — one that courts enforce against every other branch of government. Judicial review, a bill of rights with teeth, and a separately elected president make it the family member that departed furthest from the Westminster pattern.
It is also radically decentralised. Each of the fifty states has its own constitution, legislature, common law and complete court system; the federal courts form a second, parallel ladder. Most law that touches daily life — contracts, property, crime, family — is state law.
A bicameral legislature with both chambers elected: the House by population every two years, the Senate two per state for six-year terms. Legislation needs both chambers and the President's signature — or a two-thirds override of a veto.
The President is elected apart from the legislature and cannot sit in it — the sharpest break from Westminster, where the executive is drawn from and answers to the house. There is no confidence vote; the terms are fixed.
Federal judges are nominated by the President, confirmed by the Senate, and serve for life. The design buys independence at the price of high-stakes appointment battles.
Each state has its own constitution, its own elected government, its own courts and its own common law. State supreme courts — not the US Supreme Court — are the final word on what their state's law means.
Final on the federal constitution and federal law. Almost its entire docket is discretionary: from thousands of petitions for certiorari each year it selects fewer than a hundred, taking cases where the law is unsettled or the circuits disagree.
Two ladders, side by side: a case belongs to the state system or the federal one depending on what law it raises, and only federal questions can cross from a state supreme court to the US Supreme Court.
Any court, state or federal, may hold a law unconstitutional in a case before it — the question then works its way up on appeal. It is the opposite of the UK rule, and stronger than Canada's, which at least allows Parliament a notwithstanding clause.
Most states choose at least some judges by election — partisan in some, retention votes in others. Federal judges are never elected. To the rest of the common law family, judicial elections remain the most startling American feature.
The jury is constitutionally guaranteed — in criminal cases and, uniquely, in most civil cases too. Plea bargains and settlements mean few cases actually reach one, but the right shapes everything around it.
There is no single American common law: each state's courts develop their own, and they diverge. Restatements and uniform codes — like the Uniform Commercial Code — exist precisely to pull them back together.
Broad pre-trial discovery, contingency fees, and class actions make American litigation more party-driven — and higher-stakes — than anywhere else in the tradition.
The sibling that left home first. The US never shared Canada's Privy Council era, and its decisions were never binding here — but American constitutional experience mattered when Canada framed the Charter, and Canadian courts still read US authority as a comparison, often to mark where Canada deliberately chose differently.