Can missiles exercise archipelagic sea lanes passage during armed conflict at sea?

Established under the United Nations Convention on the Law of the Sea, the regime of archipelagic sea lanes passage balances the territorial integrity and national security of archipelagic States with the unimpeded and non-suspendable right of passage and overflight of foreign State vessels and aircraft. As most archipelagic States lie astride some of the world’s most important sea lines of communication, the right of archipelagic sea lanes passage is of vital strategic importance. While there is no dispute that aircraft and warships may exercise archipelagic sea lanes passage during armed conflict at sea, in contemporary naval warfare, over-the-horizon engagements using long-range missiles are now the primary, and most effective, weapons against enemy naval forces. This begs the question: Can missiles also exercise archipelagic sea lanes passage during armed conflict at sea? This article answers this question by summarizing the relevant international law surrounding archipelagic sea lanes passage and then analyses the relevant law and State practice surrounding missiles and aircraft. It argues that missiles cannot exercise archipelagic sea lanes passage during armed conflict at sea, as while they may satisfy the broad definition of aircraft, they cannot be considered military aircraft or unmanned aerial systems. However, even if they were considered aircraft, their use is inherently hostile, and therefore contrary to the prohibition of hostile acts by belligerents during archipelagic sea lanes passage in neutral waters during armed conflict at sea. This conclusion provides clarity for all States and upholds the intent of the archipelagic sea lanes passage regime.