Drop in the Ocean? Rethinking Jurisdiction in Climate Litigation

[Sude Kınık is a senior law student at Galatasaray University]

Introduction

The ECtHR’s landmark judgment in Verein KlimaSeniorinnen Schweiz and Others v. Switzerland, (“Klimaseniorinnen”) marks a significant moment in the judicialization of environmental protection through human rights frameworks. A key feature of this judgment is how the Court addressed the “drop in the ocean” argument—a common state defense in climate litigation aiming to dilute individual responsibility (Klimaseniorinnen paras 424-444, and Cannavacciuolo and Others). While this argument primarily targets questions of attribution—how a single state’s contribution can be linked to concrete climate harm—it also carries jurisdictional implications that the Court has yet to fully confront. 

By recognizing that a state may be held individually responsible for climate-related harm without needing to trace a direct causal link between its emissions and specific injuries, the ECtHR implicitly acknowledged the collective nature of climate responsibility. It accepted that attribution in climate cases can rest not on exclusive causality but on a state’s failure to discharge its due diligence obligations. This move, however, creates a tension: if the Court acknowledges that harm can arise from cumulative, multi-state conduct and that individual states can still bear responsibility, then it must also reconsider the jurisdictional limits that currently prevent applicants from holding other contributing states accountable. The “drop in the ocean” logic, while rejected as a defense to attribution, continues to operate subtly within jurisdictional doctrines, shielding other significant emitters from scrutiny simply because the applicants cannot establish jurisdictional ties.

This post argues that addressing climate harm through human rights law requires a reconceptualization of jurisdiction, one that moves beyond territorial notions and embraces a model based on effective control over the cause of the harm. Drawing on the IACtHR’s landmark Advisory Opinion Environment and Human Rights (OC-23/17), states can and should be held accountable for transboundary environmental harm when they exert effective control over harmful domestic activities, even if the victims are located abroad. Such an approach would allow the European Court to respond more coherently to the global nature of climate change and enhance access to remedies for those most affected.

The first part examines how the ECtHR in KlimaSeniorinnen addressed the “drop in the ocean” narrative through a novel interpretation of state responsibility. Second part demonstrates how this debate inevitably implicates jurisdiction, particularly in extraterritorial contexts where existing doctrines fall short. Third part explores the IACtHR’s causal-control model and related UN treaty body jurisprudence, arguing for its normative transferability to the European context.

Reframing Responsibility in Climate Litigation

The “drop in the ocean” argument centers on multi-state responsibility in climate matters. The core legal challenge, therefore, is establishing a direct causal link between a singular state’s acts and individual harm (Klimaseniorinnen para. 439) While acknowledging that climate impacts result from cumulative global actions, the Court nonetheless held that individual states could be found responsible (paras 441-443, 548) It found it adequate for applicants to demonstrate that the state’s failure to take reasonable measures had the potential to meaningfully reduce the harm or to alter its course (para. 444) If such a potential existed and the state nonetheless failed to act, this omission gives rise to its individual responsibility. This conclusion aligns with UNFCCC Article 3(3), which requires states to take precautionary measures not only after, but also in anticipation of harm—regardless of their limited individual contributions. Thus, even States with only a minor share in emissions may still be held responsible for inaction.

The Court rebutted arguments premised on the necessity of establishing a direct causal nexus between specific state conduct and the harm (paras 315, 317, 382-3, 437) Rather than requiring a clear, direct link between Switzerland’s emissions and the applicants’ health impacts, the Court adopted a more context-sensitive approach. This is particularly appropriate in the realm of climate litigation, where traditional models of causation—based on linear and temporally proximate chains of events—are often ill-suited.

Climate change, by its very nature, unfolds over extended periods of time and typically results in diffuse, indirect harms (pp. 1466-70). Individuals are not exposed to a singular act of wrongdoing, but rather to a cumulative, transboundary phenomenon resulting from the aggregated conduct of multiple actors. This challenges rigid causation standards common in human rights law. The Court, recognizing this, reframed its inquiry: instead of seeking precise causation, it asked whether the state had failed to take reasonable and proportionate measures which, if implemented, could have reduced or mitigated the harm in question. This shift towards a due diligence standard reflects evolving international environmental law and a more realistic understanding of state responsibility. However, this does not imply that there is no causal relationship between state conduct and climate damage. Rather, it acknowledges that such causality is often diffuse and complex in climate contexts, making it difficult to pinpoint direct cause-and-effect chains. The Court’s reliance on due diligence assessments does not negate causality but reframes its evidentiary basis: a state’s failure to adopt available and reasonable measures—despite having the capacity to do so—can be causally linked to the resulting harm. Thus, the causal nexus is not discarded but embedded in the evaluation of whether the state fulfilled its individual obligations. 

This doctrinal evolution invites a broader conceptual shift: from viewing state responsibility through the prism of exclusive wrongdoing to assessing it in terms of missed opportunities for prevention. What matters is not whether the state was the sole or principal contributor to the harm, but whether it failed to act when it reasonably could have. Yet, while the Court successfully addresses attribution through this lens, it leaves open the related jurisdictional challenge—namely, how victims can bring claims against states beyond their own borders.

Beyond Attribution: Jurisdictional Challenges in Climate Litigation

Beyond attribution, the “drop in the ocean” argument inevitably leads to a broader and more pressing question: Given that multiple actors contribute to greenhouse gas (GHG) emissions, can legal action be brought against each of them?

To illustrate, consider a hypothetical extension of KlimaSeniorinnen. Suppose part of the harm suffered by the Swiss applicants is attributable to an industrial zone located across the border in Germany. In this scenario, the applicants might consider naming Germany, a state party, as a co-respondent given its potential contribution to the harm. Yet, they cannot, given the jurisdictional barriers in bringing a case against Germany. Under the ECHR Article 1, they fall outside the territorial and personal jurisdiction of Germany: They neither reside in Germany nor are under its personal or territorial effective control. 

This issue is particularly salient in the context of climate justice. The world’s lowest-income countries contribute only about one-tenth of global GHG emissions yet suffer the most severe environmental consequences. A similar dilemma arises when considering applicants from states such as Eritrea. Imagine that these individuals suffer severe harm from rising temperatures and prolonged droughts, which are scientifically linked to global carbon emissions. In principle, the Eritrean applicants might wish to pursue legal action against an ECHR state with one of the highest emission shares globally. Yet, as non-residents with no direct ties to the respondent state, they fall outside its personal or territorial jurisdiction. Procedural and jurisdictional constraints prevent individuals from states like Eritrea from bringing claims before the ECtHR.

This highlights a core paradox in climate litigation: while states can now be held responsible for failing to take preventive measures within their own borders, individuals harmed by transboundary environmental effects still face jurisdictional exclusion. Those most affected by climate change—often in the Global South—are frequently those least able to access legal remedies, while major emitters remain shielded by jurisdictional doctrines grounded in territoriality. This asymmetry reveals the need to reconsider human rights jurisdiction. 

Could the jurisdictional barrier be overcome? To explore this, the jurisprudence of the Inter-American Court of Human Rights (“IACtHR”) is significant. The following section will clarify the notion of jurisdiction under international human rights and examine the IACtHR’s progressive approach.

Jurisdiction in Human Rights Context and Inter-American Court’s Approach 

In international human rights law, jurisdiction denotes the scope of a state’s obligations toward individuals, and not merely its sovereign authority. Although primarily territorial under ECHR Article 1 (M.N. and Others v. Belgium para. 99) it can extend extraterritorially. The ECtHR exceptionally recognizes its extraterritorial exercise based on “effective control” over an area (as found in Ukraine v. Russia (re Crimea)) or individuals (as found in Georgia v. Russia (II)). A new form of extraterritorial jurisdiction – “procedural control” – arises when a State exercises procedural influence over individuals, for example through judicial proceedings or international arrest warrants involving the victim (Romeo Castaño v. Belgium, paras 36-43; Markovic and Others v. Italy, paras 54-56). 

The IACtHR expanded this understanding of extraterritorial jurisdiction, recognizing a new link based on control over domestic activities with extraterritorial effect in its 2017 decision Environment and Human Rights (OC-23/17). It found that in situations involving transboundary environmental harm, a State may be considered to exercise jurisdiction over individuals located outside its territory if it maintains effective control over the domestic activities that caused the harm (paras 102, 104). This arises from a causal nexus between the State’s conduct within its own territory and the resulting rights violations abroad. Accordingly, when a State fails to regulate or prevent harmful activities within its borders—despite having the capacity—it may incur responsibility under the American Convention on Human Rights (paras 95, 97, 101). This causality-based model is especially relevant in climate litigation, where harm results from aggregated emissions, not localized incidents.

UN treaty bodies too support this broader understanding. Far before the 2017 decision, the OHCHR reported in 2009 that States’ obligations in the climate change context are not territorially confined and that they have an international duty to cooperate in realizing human rights (para. 99) Further, the Committee on Economic, Social and Cultural Rights (CESCR)’s General Comment No. 24 recognized States’ extraterritorial obligations when they can control corporate actors domiciled in their territory and/or jurisdiction whose conduct causes human rights harm abroad (paras 26, 28, 30, 31, 32). In General Comment No. 36, the Human Rights Committee similarly held that States must ensure activities under their jurisdiction—including those of corporate actors—do not cause foreseeable harm to the right to life abroad (para. 22). This obligation applies where there is a direct and foreseeable impact, even if the harm occurs outside the territory. Although these bodies do not cite the IACtHR, their reasoning mirrors its logic. Each reflects a causality-based understanding of jurisdiction: one that flows from control over harm rather than the location of the victim. 

The IACtHR’s 2017 judgment offers transferable value for Europe’s approach to environmental responsibility and jurisdiction. The ECtHR has been traditionally cautious on questions of jurisdiction, interpreting it restrictively to avoid “globalizing” its obligations (Bankovic, para. 75). With the same reasoning, in Duarte Agostinho v. Portugal and Others, the Court rejected extraterritorial jurisdiction claims against thirty-one States. The Court declined to develop a new basis of jurisdiction grounded in States’ control over climate outcomes, citing legal uncertainty and the risk of limitless obligations (paras 180-214). It insisted that the general or global effects of domestic emissions are insufficient to trigger jurisdiction under Article 1 ECHR (para. 204). However, in Klimaseniorinnen, the Court had contradicted this position by emphasizing that a direct causal link was not required for State responsibility, reflecting the shift toward the State’s due diligence obligations. Scientific advancements allow for the quantification of each State’s contribution to global emissions and climate harm, making the “closer nexus” argument less relevant.

In contrast to the ECtHR’s concern over “globalizing obligations,” Berkes argues that the IACtHR’s causal link does not require the state to exercise authority abroad, but rather enables extraterritorial jurisdiction when a state is connected to transboundary harm, has knowledge of it, and possesses the capacity to prevent it. As Tigre and Urzola underline, even without fixed causality thresholds, this standard offers a meaningful avenue for victims of transboundary environmental harm. Effectively, accepting a causality-based extraterritorial link in climate cases would not turn the Convention into a universal climate treaty, as the ECtHR fears. Rather, it would remain confined to attributing responsibility to member States for the harms they materially contribute to. The enlargement of the potentially protected group stems not from an expansion of obligations, but from the transboundary nature of climate-related harm itself. Denying jurisdiction on this basis risks reinforcing a disparity: the gap between those who suffer most from climate change and those most responsible for it. Combined with procedural barriers to access justice, such a position threatens to turn climate litigation from a rights-based mechanism into a geographically contingent privilege.

In the climate context, where emissions and consequences are rarely confined to one jurisdiction, this jurisprudence opens a path forward.

Conclusion 

Addressing climate-related human rights violations is urgent as rights cannot be protected unless individuals are alive and healthy. Since environmental diplomacy continues to fall short (here, and here), judicialization of environmental protection is essential. Recent ECtHR case law reflects a growing judicial recognition that individual states cannot evade responsibility under the “drop in the ocean” argument. This marks an important shift. Yet to fully realize climate justice, applicants must also overcome jurisdictional barriers that prevent claims from being heard. The traditional conception of jurisdiction, premised on physical proximity or direct control over victims, appears increasingly incompatible with the transnational nature of environmental harm. Jurisdictional constraints, when rigidly applied, render states unaccountable not because they are uninvolved, but because their harmful acts unfold across borders. To achieve climate justice, legal systems must adapt—not by abandoning principles of jurisdiction, but by reinterpreting them to reflect the reality that power, impact, and responsibility often transcend borders.