Why was the Mabo case so important in Australia? Which of the following is correct? The case was important because it was the first time that an aboriginal had won a significant legal case against the government in Australia The case was important because the court decided that the doctrine of terra nullius did not apply, there was a system of aboriginal law present when the English arrived in Australia The case determined that all law existing before the settlement of Australia was now supplanted by English law, which still exists today The case meant that no English law now applies in Australia, only Australian law is now relevant in determining the laws of Australia