This original action for the writs of certiorari and prohibition assails the constitutionality of Republic Act No 9522 (RA 9522) adjusting the country’s archipelagic baselines and classifying the baseline regime of nearby territories. In March 2009, Congress amended RA 3046 by enacting RA 9522, the statute under scrutiny. The change was prompted by the need to make RA 3046 compliant with the terms of the United Nations Convention on the Law of the Sea (UNCLOS), which the Philippines ratified on 27 February 1984. Among others, UNCLOS prescribes the water-land ratio, length, and contour of baselines of archipelagic States like the Philippines and sets the deadline for the filing of application for the extended continental shelf. Complying with these requirements, RA 9522 shortened one baseline, optimised the location of some basepoints around the Philippine archipelago and classified adjacent territories, namely, the Kalayaan Island Group (KIG) and the Scarborough Shoal, as 'regimes of islands' whose islands generate their own applicable maritime zones.

The petitioners, professors of law, law students and a legislator, assail the constitutionality of RA 9522 on two principal grounds, namely: (1) RA 9522 reduces Philippine maritime territory, and logically, the reach of the Philippine State’s sovereign power, in violation of Article 1 of the 1987 Constitution, embodying the terms of the Treaty of Paris and ancillary treaties; and (2) RA 9522 opens the country’s waters landward of the baselines to maritime passage by all vessels and aircrafts, undermining Philippine sovereignty and national security, contravening the country’s nuclear-free policy, and damaging marine resources, in violation of relevant constitutional provisions.

In addition, the petitioners contend that RA 9522’s treatment of the KIG as a 'regime of islands' not only results in the loss of a large maritime area but also prejudices the livelihood of subsistence fishermen. To buttress their argument of territorial diminution, the petitioners facially attack RA 9522 for what it excluded and included - its failure to reference either the Treaty of Paris or Sabah and its use of UNCLOS’s framework of regime of islands to determine the maritime zones of the KIG and the Scarborough Shoal.

Commenting on the petition, the respondent officials raise threshold issues questioning: (1) the petition’s compliance with the case or controversy requirement for judicial review grounded on petitioners’ alleged lack of locus standi; and (2) the propriety of the writs of certiorari and prohibition to assail the constitutionality of RA 9522. On the merits, respondents defend RA 9522 as the country’s compliance with the terms of UNCLOS, preserving Philippine territory over the KIG or Scarborough Shoal. Respondents add that RA 9522 does not undermine the country’s security, environment and economic interests or relinquish the Philippines’ claim over Sabah.

Held: Petition denied.

The petitioners submit that RA 9522 'dismembers a large portion of the national territory' because it discards the pre-UNCLOS demarcation of Philippine territory under the Treaty of Paris and related treaties, successively encoded in the definition of national territory under the 1935, 1973 and 1987 Constitutions. The petitioners theorise that this constitutional definition trumps any treaty or statutory provision denying the Philippines sovereign control over waters, beyond the territorial sea recognised at the time of the Treaty of Paris, that Spain supposedly ceded to the United States. The petitioners argue that from the Treaty of Paris’ technical description, Philippine sovereignty over territorial waters extends hundreds of nautical miles around the Philippine archipelago, embracing the rectangular area delineated in the Treaty of Paris.

The petitioners' theory fails to persuade us. UNCLOS has nothing to do with the acquisition (or loss) of territory. It is a multilateral treaty regulating, among others, sea-use rights over maritime zones (ie, the territorial waters [12 nautical miles from the baselines], contiguous zone [24 nautical miles from the baselines], exclusive economic zone [200 nautical miles from the baselines]), and continental shelves that UNCLOS delimits. UNCLOS was the culmination of decades-long negotiations among United Nations members to codify norms regulating the conduct of States in the world’s oceans and submarine areas, recognising coastal and archipelagic States’ graduated authority over a limited span of waters and submarine lands along their coasts.

On the other hand, baselines laws such as RA 9522 are enacted by UNCLOS States Parties to mark out specific basepoints along their coasts from which baselines are drawn, either straight or contoured, to serve as geographic starting points to measure the breadth of the maritime zones and continental shelf. Article 48 of UNCLOS on archipelagic States like ours could not be any clearer: 'Measurement of the breadth of the territorial sea, the contiguous zone, the exclusive economic zone and the continental shelf. – The breadth of the territorial sea, the contiguous zone, the exclusive economic zone and the continental shelf shall be measured from archipelagic baselines drawn in accordance with article 47.' (Emphasis supplied)

Thus, baselines laws are nothing but statutory mechanisms for UNCLOS States Parties to delimit with precision the extent of their maritime zones and continental shelves. In turn, this gives notice to the rest of the international community of the scope of the maritime space and submarine areas within which States Parties exercise treaty-based rights, namely, the exercise of sovereignty over territorial waters (art 2), the jurisdiction to enforce customs, fiscal, immigration, and sanitation laws in the contiguous zone (art 33), and the right to exploit the living and non-living resources in the exclusive economic zone (art 56) and continental shelf (art 77).

Even under the petitioners’ theory that the Philippine territory embraces the islands and all the waters within the rectangular area delimited in the Treaty of Paris, the baselines of the Philippines would still have to be drawn in accordance with RA 9522 because this is the only way to draw the baselines in conformity with UNCLOS. The baselines cannot be drawn from the boundaries or other portions of the rectangular area delineated in the Treaty of Paris, but from the 'outermost islands and drying reefs of the archipelago'.

UNCLOS and its ancillary baselines laws play no role in the acquisition, enlargement or, as the petitioners claim, diminution of territory. Under traditional international law typology, States acquire (or conversely, lose) territory through occupation, accretion, cession and prescription, not by executing multilateral treaties on the regulations of sea-use rights or enacting statutes to comply with the treaty’s terms to delimit maritime zones and continental shelves. Territorial claims to land features are outside UNCLOS, and are instead governed by the rules on general international law.

The petitioners next submit that RA 9522’s use of UNCLOS' regime of islands framework to draw the baselines, and to measure the breadth of the applicable maritime zones of the KIG, 'weakens our territorial claim' over that area. The petitioners’ argument that the KIG now lies outside Philippine territory because the baselines that RA 9522 draws do not enclose the KIG is negated by RA 9522 itself. Section 2 of the law commits to text the Philippines' continued claim of sovereignty and jurisdiction over the KIG and the Scarborough Shoal:

SEC. 2. The baselines in the following areas over which the Philippines likewise exercises sovereignty and jurisdiction shall be determined as 'Regime of Islands' under the Republic of the Philippines consistent with Article 121 of the United Nations Convention on the Law of the Sea (UNCLOS):

a) The Kalayaan Island Group as constituted under Presidential Decree No. 1596 and

b) Bajo de Masinloc, also known as Scarborough Shoal. (Emphasis supplied)

Had Congress in RA 9522 enclosed the KIG and the Scarborough Shoal as part of the Philippine archipelago, adverse legal effects would have ensued. The Philippines would have committed a breach of two provisions of UNCLOS. First, art 47.3 of UNCLOS requires that '[t]he drawing of such baselines shall not depart to any appreciable extent from the general configuration of the archipelago'. Second, art 47.2 of UNCLOS requires that 'the length of the baselines shall not exceed 100 nautical miles', save for three per cent (3%) of the total number of baselines which can reach up to 125 nautical miles. Although the Philippines has consistently claimed sovereignty over the KIG and the Scarborough Shoal for several decades, these outlying areas are located at an appreciable distance from the nearest shoreline of the Philippine archipelago, such that any straight baseline looped around them from the nearest basepoint will inevitably 'depart to an appreciable extent from the general configuration of the archipelago'.

The petitioners hold the view that, based on the permissive text of UNCLOS, Congress was not bound to pass RA 9522. We have looked at the relevant provision of UNCLOS and we find the petitioners’ reading plausible. Nevertheless, the prerogative of choosing this option belongs to Congress, not to this Court. Moreover, the luxury of choosing this option comes at a very steep price. Absent an UNCLOS-compliant baselines law, an archipelagic State like the Philippines will find itself devoid of internationally acceptable baselines from where the breadth of its maritime zones and continental shelf is measured. This is a recipe for a two-fronted disaster: first, it sends an open invitation to the seafaring powers to freely enter and exploit the resources in the waters and submarine areas around our archipelago; and second, it weakens the country’s case in any international dispute over Philippine maritime space. These are consequences Congress wisely avoided.​