How is common law changed?

Common law is changed when judges make new decisions in court or when a written law is made by Parliament that overrides common law.

Common law is developed through decisions made by judges in court. Most of the time, courts use existing laws to decide cases. But sometimes there is no existing law written by Parliament on an issue, or the law is unclear, so judges look at past decisions to help guide them. This is called precedent. If no past cases with similar circumstances exist, a new decision is made. This then becomes precedent for future similar cases and is called common law.

A court can change common law by making a new decision that sets a different precedent, but this can only happen in a higher court, such as the High Court of Australia. This means they make a new ruling that replaces the old precedent, which changes the common law.

One example of this is the Mabo Case in 1992. The High Court considered if Eddie Mabo and other Meriam people had rights to land on Mer (Murray Island). The Court found that they did, and ruled that the land belonged to the Meriam people. This decision overruled the existing common law principle of terra nullius, which had said that Australia belonged to no one before British settlement. The decision in the Mabo Case changed the common law and recognised native title in Australia.

Common law can also be changed by Parliament. Parliament can change common law by passing a new written law, called statute. If the statute covers the same issue as the common law, the statute takes priority. This means the common law no longer applies where the new statute is in force.