What is common law?

Common law in Australia is the body of law developed by judges in court decisions, rather than written by Parliament. It traces back to the English common law brought to Australia from the founding of the colony in 1788 and has been developed continuously by Australian courts ever since. The common law covers areas including contract law, tort law (such as negligence, defamation, and trespass), much of property law, judicial review, and many criminal law principles, though most criminal offences are now codified by statute.

Common law operates through the principle of precedent (stare decisis). Courts must follow the rulings of higher courts in the same hierarchy on the same legal question. The High Court of Australia is the supreme decision-maker for Australian common law, with its decisions binding on all other Australian courts. State and territory supreme courts develop common law for their jurisdictions, subject to High Court oversight. The Federal Court develops common law in areas of federal jurisdiction.

Common law and statute law interact closely. Parliament can pass legislation that modifies or overrides common law principles (for example, the Defamation Acts that modified common law defamation, the Australian Consumer Law that codified many consumer rights previously based on common law, and the various state criminal codes that have replaced common law offences). Where Parliament has not legislated, the common law continues to operate. Where the courts interpret legislation, they use common law principles of statutory interpretation.

The development of common law is incremental. Judges decide specific cases by applying existing precedents to new facts, distinguishing earlier cases where the facts differ materially, and occasionally developing new principles where existing law does not adequately address modern circumstances. The 1992 Mabo decision is a famous example of common-law development, with the High Court recognising native title for the first time and ending the legal fiction of terra nullius that had been assumed since 1788. Australian common law has gradually diverged from English common law over the past 50 years, with the High Court developing distinctly Australian doctrines in many areas. The Privy Council in London, which was previously the final court of appeal for Australian common-law matters, has had no Australian appellate role since the Australia Acts 1986.