International Law Studies


This article analyzes a 2023 maritime incident in which the Chinese Navy Ship (CNS) Ningbo employed active sonar in the vicinity of His Majesty’s Australian Ship (HMAS) Toowoomba, while knowing that Toowoomba had divers in the water. The Chinese sonar caused injuries to the Australian divers. The article discusses the employment of acoustic devices to cause harm during peacetime and analyzes whether CNS Ningbo’s actions constituted a failure of "due regard" and other applicable legal regimes and norms. The article concludes that CNS Ningbo’s actions were an unlawful use of force and failed to demonstrate due regard, and that HMAS Toowoomba could have lawfully employed necessary and proportionate measures in self-defense.