Legislation governing advance directives has been enacted in six Australian jurisdictions. As evidenced by parliamentary debates, the goal of enacting legislation was to enshrine the common law and to remove any doubt about whether a competent individual was entitled to complete an advance directive that refused life-sustaining medical treatment. The common law cases contain many judicial pronouncements about the importance of the principle of autonomy in shaping the law in this field. It should therefore follow that the principle of autonomy would also be promoted by the legislation. This article argues that the statutory regimes have, for the most part, eroded rather than promoted the principle of autonomy. While some of the statutory regulation can be justified as seeking to promote autonomous decision-making of a competent person, many of the restrictions about when an advance directive refusing treatment can be entered into or operate, or be disregarded by medical professionals, have effectively undermined an individual's ability to ensure that her or his refusal of medical treatment at the end of life is followed.