The legal authority to make decisions about withdrawing life-sustaining treatment depends on the patient's competence and wishes. For incompetent patients, legally authorized decision-makers include substitute decision-makers like family or an advance directive. In Australia, decisions must consider the patient's best interests based on values, goals, and medical recommendations. In complex cases, courts may provide guidance. Withdrawing treatment requires consent from competent patients or substitute decision-makers considering the patient's wishes and best interests.