The International Court of Justice’s (ICJ) recent advisory opinion on climate change is a landmark in the development of international law. In this post, we focus on a short section of the opinion that may signal a fundamental shift in how international law conceives of statehood. We aim to decipher the ICJ’s “Delphic pronouncement” (Judge Tomka) on sea-level rise and its implications for the statehood of low-lying island States.

In classical international law, statehood (the most fundamental type of international legal personality) is defined by three cumulative criteria: territory, population, and government (see Shaw, p. 182). These criteria reflect customary international law and, along with a fourth criterion on the capacity to conduct foreign relations, were codified in the Montevideo Convention on the Rights and Duties of States (the “Montevideo criteria”).

What could not have been foreseen during the initial development of these criteria was the complete submersion of a State’s (land) territory beneath the sea. But that is now a very real possibility. 

For low-lying island States in particular, sea-level rise due to climate change poses an existential threat. The United Nations Development Programme predicts that 95% of Tuvalu’s land will be flooded by 2100. Tuvalu and Vanuatu have identified sea-level rise as their greatest national security threat and have engaged in extensive diplomatic advocacy to generate attention on the issue (see Green and Guilfoyle, p. 686-687). These efforts contributed to the United Nations General Assembly’s decision to seek the ICJ’s advisory opinion on climate change.

The central question we address in this post is this: What becomes of statehood when a State’s entire territory disappears beneath the sea? The intuitive answer would be: no territory, no state (cf. Shaw, p. 190: “the disappearance, like the existence, of a state is a matter of fact”; Gerrard, p. 584). However, the ICJ took a different turn in its opinion.

The ICJ’s Position on Sea-Level Rise and Statehood

Although the question of statehood was not explicitly included in the General Assembly’s request, the ICJ nonetheless addresses it – albeit briefly and not in the operative part, but in a single paragraph, nestled in the 140-page document:

“363. Several participants argued that sea level rise also poses a significant threat to the territorial integrity and thus to the very statehood of small island States. In their view, in the event of the complete loss of a State’s territory and the displacement of its population, a strong presumption in favour of continued statehood should apply. In the view of the Court, once a State is established, the disappearance of one of its constituent elements would not necessarily entail the loss of its statehood.”

Unfortunately, the ICJ offered no reasoning for this view – possibly reflecting internal disagreement (see the contribution by Syla and Kent). However, the last sentence suggests the ICJ’s general agreement with the findings of the International Law Commission (ILC) on the issue. In its May 2025 final report on sea-level rise in relation to international law, the ILC took a clear position in favor of continuing statehood even after the complete loss of territory, declaring:

“35. With regard to States particularly affected by climate change-related sea-level rise, there is strong support among States for the continuity of statehood and sovereignty and the maintenance of international legal personality and membership of international organizations.”

It remains unclear whether the view of the ILC represents lex lata or rather, as suggested by Judge Tomka and legal scholars De Spiegeleir and Rocha, a progressive development of the law due to the urgent realities of climate change. Notably, there is – as yet – no State practice addressing the complete submersion of territory (see below).

Discussion of Statehood in Separate Declarations

While the ICJ’s advisory opinion was unanimous, a majority of judges appended separate opinions or declarations. Four of these address the issue of statehood. Judges Aurescu (paras. 20-24), Bhandari (para. 7), and Sebutinde (para. 8) explicitly endorse the ICJ’s position and advocate for an even stronger stance in favour of continued statehood.

Judge Aurescu, formerly a member of the ILC’s study group on sea-level rise, takes the strongest stance in favor of those States endangered in their existence. He sees a clear rule of continuing statehood, based on the principle of legal stability, and argues for an obligation of third states to recognize the continued statehood and maritime entitlements of “de-territorialized” States (paras. 20, 23). Judges Aurescu and Bhandari propose that restitution could include the “continued recognition by all States of the entitlements of States affected by sea-level rise to their current maritime zones as well as of their continued statehood, even if submerged.” (Aurescu, para. 24; cf. Bhandari, para. 7). This is particularly interesting because restitution presupposes wrongful conduct – an aspect elaborated on by the ICJ in substantive parts of the opinion (on the role of state responsibility in the ICJ’s advisory opinion, see Paddeu and Jackson, Wewerinke-Singh and Vinuales, and Reetz).

In contrast, Judge Tomka, in his declaration, voices criticism of the ICJ’s light-handed approach to the topic. He rightly points to the fundamental importance of the notion of statehood to international law and the far-reaching implications any change of the law in this regard might have (para. 2). Judge Tomka reiterates the general view that “statehood is virtually inseparable from a land and a people” (para. 3) and refutes the view that the Montevideo criteria apply only to the original creation of States, not their continuing existence as such. He also calls for caution in accepting the ILC’s conclusion as existing customary international law (para. 6) and highlights the exceptional relevance of (land) territory to statehood, sovereignty, and self-determination in international law (paras. 7-9).

The Limited Value of Precedent

As Judge Tomka observes in his declaration, concerning State practice on the issue of submerged States, “on a narrow view, there is none” (para. 5). Perhaps the closest “precedent” takes us back over 200 years: when the Order of Malta lost control of Malta and thus of its territory but retained its international legal personality. The Order of Malta is a subject of international law sui generis – not a State, but mostly treated as such (see Shaw, p. 224). It enjoys State and other forms of immunity, maintains embassies, issues diplomatic passports, and concludes treaties. Yet its non-State status limits its value as a precedent for de-territorialized statehood (see Allen and Prost).

A more recent and legally significant step came in August 2024, when Tuvalu and Australia concluded the Falepili Union treaty. This international agreement recognizes the dangers of climate change to Tuvalu’s existence and aims to address these concerns by explicitly recognizing the continuing statehood and sovereignty of Tuvalu (Article 2(b)) and including a human mobility scheme for Tuvaluans to move to Australia (Article 3). More than 80 percent of the population of Tuvalu has since applied for climate change visas. Legally, this treaty is best understood as pre-emptive opinio juris, not State practice as such. The reactions of States to the first actual submersion of a State will be decisive – if a uniform position emerges, it may constitute  “instant customary law.”

Subsequent Issues of “De-Territorialized” Statehood

The ICJ did not elaborate on the legal consequences of its presumption of continuing statehood, beyond a general duty to cooperate (para. 364, see De Spiegeleir/Rocha). In the event of complete loss of territory, such a duty might oblige third States to take specific measures, but the opinion provides little further guidance.

The ILC, by contrast, outlined numerous legal and political reasons for accepting the continuing statehood of submerged States: legal stability and certainty, territorial integrity, permanent sovereignty over natural resources, self-determination of peoples, and equity (paras. 38-39). Yet, as Judge Tomka emphasizes in his declaration, territory is still fundamental to the very concept of statehood (paras. 3 and 8). The exercise of extraterritorial jurisdiction is the exception, not the rule. What, then, is the jurisdictional anchor of these States in the rough waters of international law?

Transitional or Permanent?

A key question is whether continued statehood would be permanent or merely transitional. The ICJ’s vague formulation in paragraph 363 of the opinion leaves open the circumstances under which statehood would be lost or preserved. This ambiguity allows for the interpretation that continued statehood may be understood as a “transitional phase.”

While not identical, there have been comparable cases where territory became uninhabitable and the population had to resettle elsewhere. As described by Rayfuse, in the 1870s, about half of Iceland’s territory became uninhabitable due to a volcanic eruption, and large parts of the population resettled in Canada. However, “New Iceland eventually joined the province of Manitoba becoming fully integrated into Canada” (Rayfuse, p. 8). Whereas such incorporation is one possible scenario, a State could alternatively turn into another legal subject over time: Once the entire population resettles in a different jurisdiction, the submerged State might (similar to the Order of Malta) continue to entertain diplomatic missions and be a member of international organizations – ultimately evolving into a sui generis subject of international law. 

Territory: Maritime Zones As a Sovereignty “Anchor”

Traditionally, maritime claims are tied to the territory of the coastal State (cf. Articles 2-16 United Nations Convention on Law of the Sea). While both the ILC (para. 29) and the ICJ (para. 362) have come to the conclusion that States are not under the obligation to update their “charts or lists of geographical co-ordinates that show the baselines and outer limit lines of their maritime zones,” neither body explicitly affirms the permanence of these baselines (see also De Spiegeleir and Rocha). The future of the maritime zones of the sinking State thus remains uncertain.

However, it would not only be unjust to deprive sunken States of maritime entitlements (as Judge Aurescu argues, para. 23), but these could also serve as an “anchor” for continuing statehood. In the absence of landmass, the sunken State could continue to exercise its sovereignty over its maritime area. Further, when States that are highly vulnerable to sea-level rise negotiate with other States about possible human mobility schemes, they could use their maritime claims and connected fishing and exploitation rights as leverage (cf. Gerrard, pp. 598 et seq.).

Population: Citizenship and Statelessness

James Crawford has noted that the “permanent population” criterion for statehood “is not a rule relating to the nationality of that population.” However, without territory, there can hardly be a permanent population. In order to preserve the de-territorialized State’s statehood and because so far, the statehood criteria have been largely defined from a “territorial” view (see Crawford), the remaining criteria will also have to be interpreted in a new light.

One main concern with a possible disappearance of statehood is the issue of statelessness, which must be prevented (see e.g. the 2009 submission by the United Nations High Commissioner for Refugees on Climate Change and Statelessness; ILC, para. 38). While international law allows for multiple citizenships, the question remains: What would be the role of the de-territorialized citizenship and what rights would it confer, especially considering the de-territorialized State’s limited ability to exercise jurisdiction? In recent  years, the idea of virtual copies of endangered States – such as 3D scans of their territory uploaded to the metaverse – has emerged (e.g., by Tuvalu). One of the main values of such “virtual States” could be the preservation of the State’s cultural heritage. When displaced citizens acquire a second citizenship, the de-territorialized State’s citizenship could similarly be limited to a “commemorative nationality”.

Government: Self-determination vs. Sovereignty

To enable the effective exercise of governmental functions in a future de-territorialized State, Tuvalu “started exploring a digital ID system, which will use the blockchain to connect the Tuvaluan diaspora and allow them to participate in Tuvaluan life, wherever they are.” The role of government in a “sunken” State could be to maintain connections between its diaspora and the government itself, as well as within the diaspora community.

Whereas the host State would exercise sovereignty over its territory, displaced people would continue to have a right to self-determination. To remain represented by a government, however, a de-territorialized State would have to find a new seat of government (or at least a location  to host its servers) (for more in depth analysis, see Mitra and Sanghi). As the exercise of regular governmental functions would probably fall outside the scope of permitted diplomatic activity (see Article 3 Vienna Convention on Diplomatic Relations), a specific agreement between the host State and the ex situ government would be advisable. Due to the prohibition of intervention, the ex situ government would be severely limited in exercising jurisdiction without the host State’s consent.

Even with consent, an unsolved problem could be the emergence of dual jurisdiction: While  the host State’s citizens would be governed solely by its jurisdiction, resettled communities would additionally be governed by the sunken State’s (extraterritorial) jurisdiction. They would thus have to follow the rules of both States but have fewer rights than “territorial” citizens (as pertains to voting, for example). Hence, people from a sunken State would be in a permanent situation of being foreigners everywhere. This could lead to double-standards and neo-colonialist power structures (for third world approaches to climate change law, see Atapattu and Gonzalez). Potentially, the displaced people could become a recognized (autonomous) minority in their host State.

The Imperative to Prevent

Following the ICJ’s opinion, only time will tell whether the Montevideo criteria are themselves “sinking,” and what might replace them. It remains doubtful whether sunken States could be sovereign equals to States with territory, as they would necessarily rely on the goodwill of their host State to cede jurisdiction to some degree. Even though the ICJ’s opinion is a big step forward (especially) for small island States, it cannot, by itself, preserve a State’s full sovereignty once its territory is submerged.

Small island States have contributed the least to climate change, yet now face an existential threat. This unfair fate must be prevented. If their territory is lost to the sea, an essential part of their sovereignty and self-determination would too be swept away beneath the waves.