Can Island Nations Secure Fixed Baselines under International Law? Part I – Jindal Forum for International and Economic Laws
Introduction
The 21st century, heralded for its unprecedented surge in technological advancements, is currently confronted with a malignant phenomenon termed ‘climate change’. Extreme weather, global warming, and the ensuing rise in sea levels are now very much a ubiquitous reality. Among its various negative impacts, one particularly distressing reality is the swallowing of territory of coastal States, especially island nations, due to rising sea levels. In addition to endangering the region’s physical infrastructure and inhabitants, it also has legal ramifications that are now upsetting the international legal community. The shifts of these coastlines inwards cause an analogous inward movement of maritime boundaries, including the territorial sea, exclusive economic zone (EEZ), and continental shelf, as defined under the United Nations Convention on the Law of the Sea (UNCLOS). This retreat disproportionately impacts the EEZ of such countries, where States exercise sovereign rights over marine resources.
The EEZ is a region of 200 nautical miles (nm) in the sea from the baseline of a country where the State has exclusive rights over exploration and utilisation of marine resources. States’ coastal regions may experience excessive flooding due to sea level rise, posing an imminent threat to their coastline. This shifts the coastline inwards, which causes the retreat of the country’s EEZ. Small island nations are known to be the most susceptible to these shifts.
Pacific nations, including Tuvalu, Kiribati, and the Marshall Islands, are projected to face functional uninhabitability by 2030–2040 due to saltwater intrusion, coastal erosion, and freshwater scarcity. They are likely to lose more than half of their present EEZs, threatening both territorial sovereignty and economic survival. Studies indicate that 40% of the Marshall Islands’ infrastructure could be chronically flooded by 2030, Tuvalu’s groundwater may become undrinkable within this timeframe, and Kiribati’s government has already begun planning for large-scale displacement by mid-century, underscoring the existential urgency of these climate impacts. Climate change is projected to strip the Pacific islands of a staggering 41.5% of their combined EEZ area by mid-century. It is a catastrophic blow to marine resources, sovereign rights, and the survival of vulnerable coastal communities that depend on these waters for their cultural and economic identity.
To counter this, an alternate interpretation of the UNCLOS was brought up by the Pacific island countries. Article 5 defines the normal baseline as the “low-water line along the coast as marked on large-scale charts officially recognized by the coastal State.” The Pacific Islands Forum, in its Declaration on Preserving Maritime Zones in the Face of Climate Change-Related Sea-Level Risedeclared that the treaty does not make it obligatory to continuously update the baselines. Rather, these countries can permanently set their maritime baselines as they currently exist, as affirmed by the Pacific Islands Forum’s 2021 Declaration on Preserving Maritime Zones in the Face of Climate Change-Related Sea-Level Rise. Article 57 of UNCLOS states that the EEZ will extend to “200 nm from the baselines from which the breadth of the territorial sea is measured.” Under Article 75the State must deposit a copy of the charts or geographical coordinates of the outer limits of the EEZ with the Secretary-General of the UN. Hence, there is an absence of any explicit mandate for the baselines to be ambulatory; instead, they can be fixed to annul the deleterious effects of climate change.
This interpretation gains traction when examining the drafting history of UNCLOS. The omission of a requirement in Article 75 (notably, the lack of an obligation for States to continuously update nautical charts depicting the ‘normal baseline’ under Article 5) demonstrates an intentional exclusion of ambulatory baselines. For instance, Article 75 only mandates the deposit of charts or coordinates defining the EEZ’s outer limits but does not prescribe periodic revisions to reflect coastal changes. This silence suggests that the drafters did not envision baselines shifting dynamically with geographical alterations, thereby leaving room for fixed baselines to preserve maritime entitlements against climate-induced erosion. However, this view remains contentious, as opponents counter that Article 5’s reference to the ‘low-water line’ inherently ties baselines to physical coastlines, implying ambulatory intent absent explicit textual support for permanence.
While this interpretation of the treaty retains a degree of legitimacy, recent developments suggest a shifting discourse. Notably, the International Law Commission (ILC) and International Law Association (ILA) in 2023 and 2024, respectively, observed that no State has formally contested the legal viability of fixed baselines under UNCLOS. The fixed baseline approach reduces their access to the high seas by negating the effects of climate change. However, the primary question is whether this interpretation is viable with the legal framework and principles of Customary International Law and the UNCLOS. This research article aims to evaluate the claims of these countries based on principles and doctrines of international law, with a focus on the valid application of the Vienna Convention on the Law of Treaties (VCLT). This article examines (1) States’ good faith obligation, (2) the fixed baseline approach’s validity as 3, and (3) its validity as Customary International Law (CIL).
Good Faith Obligation vs Geographical Reality
The island countries, especially in the Pacific, have contended that the UNCLOS does not expressly proscribe the parties from fixing the maritime boundaries, since Article 5 of UNCLOS can be construed to encompass either the coastline or the charted baseline. Nevertheless, analyzing this assertion would indicate that the ‘officially recognized’ map ought to accurately represent the coastline, as coastal States might otherwise disincentivize updating their maritime charts and boundaries. However, this risk may be overstated in practice. As highlighted in the ILC’s 2023 report, nautical charts submitted by States to depict baselines under UNCLOS are distinct from those used for navigation. The former serve a legal function to demarcate maritime zones, while operational navigation relies on updated hydrographic surveys and real-time data. Consequently, discrepancies in baseline charts do not inherently pose significant risks to maritime travel or trade.
Historically, the United States opposed this practice, characterizing it as a ‘maritime risk’ that could undermine navigational safety. However, in 2022, the U.S. explicitly revised its stance, declaring that it recognizes new trends are developing in the practices and views of States on the need for stable maritime zones in the face of sea-level rise. It further committed to work with other countries toward the goal of lawfully establishing and maintaining baselines and maritime zone limits and will not challenge such baselines and maritime zone limits that are not subsequently updated despite sea-level rise caused by climate change. This reflects a mal-intentioned interpretation of the treaty, which goes against the provisions of the VCLT. Article 31 requires the States to interpret a treaty in “good faith” and give the terms their “ordinary meaning” in its context.
The evolution of the concept of States’ sovereignty over maritime resources clearly shows that the intention of the treaty makers was to allow the States to accrue resources up to a certain limit from its actual coastlines. Even an equitable measure does not justify fixing baselines and being ignorant of real changes in geography. However, proponents of the fixed baseline approach argue that equity and fairness under international law demand a departure from strict geographical literalism. Small island States, which contribute minimally to greenhouse gas emissions, face existential threats from sea-level rise caused disproportionately by industrialized nations. The principle of common but differentiated responsibilities (recognized in climate agreements like the Paris Agreement) underscores that States bearing historical responsibility for climate harm should not benefit from the consequent erosion of vulnerable nations’ maritime entitlements.
Moreover, UNCLOS itself incorporates equity in its preamblewhich emphasizes the need for a legal order that promotes ‘equitable and efficient utilization’ of marine resources. In Maritime Delimitation in the Black Sea (Romania v. Ukraine)the ICJ affirmed that equity plays a role in maritime disputes where strict application of rules leads to unjust outcomes. Similarly, fixing baselines could be seen as an equitable adjustment to preserve the permanent sovereignty of island nations over resources they have historically depended on, even as their physical territories diminish.
Another argument raised by coastal States invokes Article 7(2) of UNCLOS, which permits the use of straight baselines in specific geographical contexts where a coastline is “highly unstable” due to natural conditions such as deltas or extreme coastal irregularities. However, this provision is narrowly tailored to address temporary or cyclical geographical instability, not the gradual, permanent effects of climate change-induced sea-level rise. Article 7 applies exclusively to the methodology for drawing straight baselines (as opposed to normal baselines under Article 5), which are already an exception requiring strict geographic justification under UNCLOS. However, this argument is unfounded since the provision clearly relates to natural conditions that cause frequent fluctuations in the coastlines of a State, causing difficulty in its preciseness.
While climate change is a gradual process overall, the Intergovernmental Panel on Climate Change (IPCC) has documented accelerated sea-level rise, with rates increasing from 1.3 mm annually (1901–1971) to 3.7 mm annually (2006–2018). The International Law Commission (ILC) Special Rapporteur has characterized such impacts as a ‘disaster’ threatening territorial integrity. These rapid changes, however, do not equate to the ‘frequent fluctuations’ contemplated under Article 7(2) of UNCLOS, which pertains to natural instability (e.g., erosion from seasonal tides) rather than irreversible, climate-driven submersion.
Furthermore, while the Tribunal in In the Matter of The Bay of Bengal Maritime Boundary Arbitration acknowledged the relevance of equitable principles in maritime delimitation, the International Tribunal for the Law of the Sea (ITLOS) and the International Court of Justice (ICJ) have consistently emphasized the primacy of ambulatory baselines under UNCLOS. For instance, in Maritime Delimitation in the Black Sea (Romania v. Ukraine)the ICJ reaffirmed that maritime zones must reflect ‘actual coastal geography’, and ITLOS, in Dispute Concerning Delimitation of the Maritime Boundary (Ghana/Côte d’Ivoire)upheld the dynamic nature of baselines as tied to physical coastlines.
These rulings align with the UNCLOS framework, which presupposes that baselines adjust to natural changes, including those exacerbated by climate change. While the ILA Expert Committee on Baselines initially concluded in its 2012 report that coastal baselines are ‘ambulatory’ as a matter of general international law, subsequent ILA resolutions in 2018, 2022, and 2024 have consistently reaffirmed that fixed baselines. Particularly in the context of climate-driven sea-level rise, are compatible with both UNCLOS and evolving customary international law. Therefore, the fixed baseline approach is a breach of the “good faith” obligation of State-parties.
In this part, I argue that the fixed baseline approach violates the good faith obligation under UNCLOS, as it contradicts the treaty’s ordinary meaning and intent by disregarding actual coastal geography. While equity and climate justice are invoked, such interpretations risk distorting UNCLOS’s foundational principles and legal coherence. Part II evaluates whether the fixed baseline approach qualifies as valid subsequent practice or customary international law, ultimately concluding it lacks sufficient state support, opinio juris, and legal coherence.
Kshitij nair is a final year law student at Jindal Global Law School.
Picture Credit: Ministry of Justice, Communication and Foreign Affairs Tuvalu Government/ REUTERS