In March 2022, the Philippines summoned China’s ambassador in Manila to protest the lingering presence of a People’s Liberation Army Navy ship in the archipelago’s southern waters in the Sulu Sea. Beijing claimed that the ship was exercising the right to pass through those waters in a “continuous and expeditious” manner, or what the UN Convention on the Law of the Sea (UNCLOS) calls “innocent passage”.
The Philippines is an archipelagic state as defined in the UNCLOS. This means that, in addition to innocent passage, its waters are also subject to the rules governing archipelagic sea lanes passage, which covers “rights of navigation and overflight” exclusively for “continuous, expeditious and unobstructed transit” from one part of the high seas to another, or from one part of a country’s exclusive economic zone to another. As its name suggests, this type of passage is exercisable through archipelagic sea lanes, or routes designated by the Philippines under the sea lanes designation procedure of the International Maritime Organisation (IMO).
At the time of the incident, however, the Philippines had yet to identify where its archipelagic sea lanes were. Thus, under Article 53 of the UNCLOS, all foreign vessels and aircraft could exercise the right of archipelagic sea lanes passage “through the routes normally used for international navigation”. The language of Article 53 leaves vast swathes of Philippine archipelagic waters virtually open to international vessel traffic – including warships – which can pass those waters without notifying the Philippine government.
The 2022 incident renewed interest in a sea lanes measure, which has languished in a Duterte presidency that downplayed Philippine gains from the 2016 South China Sea Award.
By enacting the twin measures, the Philippines can be seen as attempting to inflict what legal scholar Douglas Guilfoyle calls a “legitimacy penalty” on Chinese acts and statements that are incompatible with the UNCLOS.
Seeking to prevent a repeat of the 2022 incident, the Philippines this month passed the Philippine Archipelagic Sea Lanes Act (ASLA) and the Philippine Maritime Zones Act (MZA) in November 2024. At the ceremonial signing, which ends decades of legislative deadlock, Philippine President Ferdinand Marcos Jr stated that the twin measures “align our domestic laws with international law, specifically the [UNCLOS], improve our capacity for governance, and reinforce our maritime policies for economic development, and for national security”.
The key feature of the ASLA is a provision limiting the largely unencumbered passage and overflight of foreign vessels and aircraft to three general routes (referred to as “axis lines”) within Philippine archipelagic waters: one in the north through the Balintang Channel and two in the south, via the Sulu Sea. While the ASLA identifies the general course of the axis lines, it leaves the designation of their specific coordinates to the President of the Philippines, who has one year to consult with the IMO and the International Civil Aviation Organisation “with a view towards the adoption of [archipelagic] sea lanes and air routes”.
China has condemned the new laws and summoned the Philippine ambassador soon after the enactment of the twin measures. In a statement, Beijing denounced the laws for “illegally” including Scarborough Shoal and “most of the islands and reefs’” of the Spratlys, and for being “incompatible” with international law . The day after the signing of the laws, China published what it regards as the baselines of the territorial sea around Scarborough Shoal.
The enactment of the ASLA marks a dramatic turnaround from the position of the Philippines in 1984, when it ratified the UNCLOS with a substantive reservation on the application of the rules on archipelagic sea lanes passage to the Philippines. Prior to the UNCLOS, the Philippines had advocated for the position that all archipelagic waters are internal waters which could be closed unilaterally to foreign vessel traffic. The Philippine reservation provoked numerous protests, including from the US, Russia, and Australia.
Since the UNCLOS was adopted in 1982, its provisions on what makes up an “archipelagic state”, its boundaries, entitlements, and obligations relating to the passage of foreign vessels and aircraft, have been thought to be beyond disagreement. But in the following decades, Philippine lawmakers have continued to debate what constitutes the “Philippine Archipelago” and whether its boundaries include Bajo de Masinloc and the Kalayaan Island Group in the West Philippine Sea (designation for the South China Sea that now appears in Section 2, MZA). These features are located at a significant distance from the main island grouping.
These debates – which led to a 2009 law on archipelagic baselines and a 2011 Supreme Court decision – have been described as part of a larger effort to “put our house in order” by harmonising the archipelagic boundaries of the Philippines with the relevant provisions of the UNCLOS. Along with the South China Sea tribunal’s finding that the Philippines “could not declare archipelagic baselines surrounding the Spratly Islands”, the result has been a significantly diminished role for the UNCLOS concept of the archipelago as a legal tool for the assertion of Philippine maritime entitlements in the South China Sea.
And yet, by enacting the twin measures, the Philippines can be seen as attempting to inflict what legal scholar Douglas Guilfoyle calls a “legitimacy penalty” on Chinese acts and statements that are incompatible with the UNCLOS, such as the claim that the Spratlys form an offshore archipelago of China. To recall, the South China Sea award declared that China’s wide-ranging claims to the South China Sea based on the “nine-dash line” are “contrary” to the UNCLOS.
With these recent developments in Philippine law, it seems the Chinese and Philippine positions have shifted. Strangely, it is now China which uses a concept of archipelagos, albeit contrary to international law, to assert territorial and maritime claims – not unlike how the Philippines had done in the past before the advent of the UNCLOS.
This article is part of the Blue Security project led by La Trobe Asia, University of Western Australia Defence and Security Institute, Griffith Asia Institute, United States Studies Centre, UNSW Canberra and the Asia-Pacific Development, Diplomacy and Defence Dialogue (AP4D). Views expressed are solely of its author/s and not representative of the Maritime Exchange, the Australian government, or the collaboration partner country government.
