USNS Impeccable incident illustrates the ambiguities inherent in UNCLOS clause on military activities

In March 2009 in the South China Sea, five Chinese vessels surrounded the unarmed USNS Impeccable, a United States (‘US’) Navy ocean surveillance vessel, and ordered it to leave the area.¹ The Impeccable had been conducting routine seabed mapping and tracking submarines about seventy-five nautical miles (nm) south of China’s Hainan Island.² Two of the Chinese vessels moved within eight meters of the US ship, forcing it to take collision-avoidance measures.³ The Impeccable withdrew from the area but returned the following day accompanied by a US guided missile destroyer for its protection.⁴ This incident raised tensions in Sino-American relations as both nations accused the other of violating international law.⁵ The Pentagon protested the aggressive ‘harassment’ of the Chinese vessels while Beijing accused the US ship of illegally operating in China’s Exclusive Economic Zone (EEZ).⁶ This issue is unlikely to be resolved because the two sides fundamentally disagree on what military activities are permissible in another state’s EEZ.⁷

The Impeccable confrontation is a good example of the uncertainty and controversy regarding the legality of military operations in the EEZ. Did the United States have the right to conduct activities in China’s claimed EEZ? Was China out of line to require prior notification and permission? What does the United Nations Convention on the Law of the Sea (UNCLOS or the Convention) permit and prohibit in terms of military activities in the EEZ? Unfortunately, the issue of the military uses of the oceans in peacetime raises many contentious questions and very few answers.