Executive Summary
Overview
The governance of international watercourses has long been constrained by the tension between the shared physical reality of a transboundary river and the traditional insistence on exclusive territorial sovereignty. The community of interest principle resolves that tension by conceiving of a watercourse not as a resource divisible along territorial lines but as a single integrated system giving rise to reciprocal rights and continuing obligations among all riparian states. First articulated in the River Oder case and later broadened in Gabčíkovo–Nagymaros, the principle is now reflected in the framework of the 1997 UN Watercourses Convention and the 1992 UNECE Water Convention. Yet its practical force remains uncertain: the disputes surrounding the Indus Waters Treaty, the Grand Ethiopian Renaissance Dam, and the Mekong Basin each demonstrate that the principle constrains state behaviour only where it is supported by robust institutions, the participation of all affected states, and an acceptance that cooperation is a legal obligation rather than a matter of political discretion. For Pakistan, as a downstream riparian state, the principle nonetheless offers a valuable normative foundation, one it should consistently affirm in its diplomatic practice, reinforce through stronger enforcement institutions such as the Permanent Indus Commission, and advance as the basis for the integrated management of shared river basins.
Policy Recommendations for Pakistan
- Affirm the principle: Pakistan should consistently invoke the community of interest principle, alongside the principles of equitable and reasonable utilization and the obligation not to cause significant harm, as established norms of general international law in its diplomatic practice and multilateral engagement. Sustained and consistent reliance on these principles contributes to the development of state practice and opinio juris, reinforcing their status as settled rules of international law.
- Strengthen enforcement institutions: As the effectiveness of the community of interest principle depends on the institutional frameworks through which it is implemented, Pakistan should advocate for the strengthening of the Permanent Indus Commission (PIC). The goal should be to transform this institutional mechanism from an abstract legal principle into a framework of enforceable obligations.
- Resolve normative indeterminacy: Neither the Convention on the Law of the Non-Navigational Uses of International Watercourses (1997) (UN Watercourses Convention) nor the Convention on the Protection and Use of Transboundary Watercourses and International Lakes (1992) (UNECE Water Convention) explicitly defines the relationship between the principles of equitable and reasonable utilization and the obligation not to cause significant harm. This ambiguity leaves states with considerable discretion, creating opportunities for more powerful upstream states to advance interpretations that favour their interests. Pakistan should therefore support initiatives through the International Law Commission, United Nations forums, and model treaty development to clarify the interaction between these principles, as greater legal certainty would strengthen the position of downstream riparian states. Such efforts should also be guided by the community of interest principle, which reinforces the understanding that shared watercourses must be governed through cooperation, mutual restraint, and the protection of the collective interests of all riparian states.
- Ensure sustainable development of the shared watercourse: Pakistan should advocate for the application of the community of interest principle as the basis for integrated river basin management in international water law. Shared river basins should be governed as unified systems through basin-wide planning, joint management institutions, and coordinated environmental protection measures, rather than through fragmented, state-centric approaches.
Reimagining Sovereignty: The ‘Community of Interest’ Principle in Transboundary Water Governance
Introduction
When a watercourse flows across or forms the boundary between multiple states, the reality of a shared natural resource comes into tension with the traditional legal concept of exclusive territorial sovereignty. This tension has historically been reflected in two opposing legal approaches. Under the theory of absolute territorial sovereignty an upstream State claims an unfettered right to use the water within its territory regardless of downstream effects. Under the opposite theory of absolute territorial integrity, a downstream State claims a right to the continued, undiminished flow of the river.
Between these two extremes lies the doctrine of limited territorial sovereignty, under which each riparian state is entitled to utilize the shared watercourse, provided that its use respects the corresponding rights and interests of other riparian states. This approach recognizes that sovereignty over international watercourses is qualified by reciprocal rights and obligations, requiring states to balance their own developmental needs with the equitable utilization of the shared resource and the duty to avoid causing significant transboundary harm.
At the opposite end of the spectrum from state-centred conceptions of sovereignty is the community of interest principle, which views an international watercourse as a single, integrated natural system giving rise to a community of shared rights and responsibilities among all riparian states. Rather than treating the river as divisible along territorial lines, the principle emphasizes cooperation, joint management, and the collective stewardship of the basin. This reflects the understanding that the sustainable governance of shared water resources depends upon coordinated action rather than unilateral control.
The Community of Interest in Shared Watercourses
The classical formulation of the community of interest principle is found in the Permanent Court of International Justice’s 1929 judgment in the River Oder case. Faced with competing claims by riparian states, the Court concluded that the shared nature of an international river gives rise to a corresponding community of legal interests. The Court concluded that,
“This community of interest in a navigable river becomes the basis of a common legal right, the essential features of which are the perfect equality of all riparian States in the user of the whole course of the river and the exclusion of any preferential privilege of any one riparian State in relation to the others.”[1]
Almost seventy years later, in the 1997 Gabčíkovo–Nagymaros case, the International Court of Justice revived and expressly broadened the principle. It held that the community-of-interest concept was not confined to navigation but extended to the non-navigational uses of an international watercourse, and it linked the principle to the modern requirement of equitable and reasonable sharing.[2] The earlier Lake Lanoux arbitration had already established the corollary that an upstream State, though free to develop, may not simply disregard the interests of its co-riparians.[3]
These judicial principles are reflected in two framework treaties. The 1997 Convention on the Law of the Non-navigational Uses of International Watercourses (Watercourses Convention) codifies the twin rules of equitable and reasonable utilisation and the obligation not to cause significant harm, together with duties of prior notification and cooperation.[4] The 1992 Convention on the Protection and Use of Transboundary Watercourses and International Lakes (UNECE Water Convention), now open to States beyond Europe, builds a similar cooperative architecture around shared basins.[5] Neither Convention has achieved universal ratification, and both leave unresolved one of the central questions of international water law: how the principle of equitable and reasonable utilization should be reconciled with the obligation to prevent significant transboundary harm. Nevertheless, taken together, they demonstrate that the community of interest principle has evolved from a judicially articulated principle into a codified normative framework underpinning the governance of international watercourses.
The Community of Interest in Practice
The practical significance of the community of interest principle ultimately depends on whether it is capable of constraining state behaviour in situations of heightened political and strategic sensitivity. Three contemporary disputes, each reflecting a different model of transboundary water governance, demonstrate both the principle’s potential and its limitations.
The Indus Waters Treaty
The Indus Waters Basin is governed by the 1960 Indus Waters Treaty that allocates the eastern rivers to India and the western rivers primarily to Pakistan. The Treaty also provides an elaborate mechanism for resolving disputes.[6] However, this treaty regime is now under acute strain. India declared the treaty to be ‘in abeyance’ in April 2025 and has reaffirmed that position since; a Court of Arbitration issued a further award in May 2026, which India rejected as null and void while contesting the tribunal’s legitimacy, and which Pakistan invoked as confirmation that the treaty remains valid and binding.[7] The dispute crystallises a doctrinal problem as the treaty contains no provision for unilateral “abeyance”. India frames its step as a withdrawal of cooperative goodwill in response to cross border terrorism; Pakistan and the tribunal treat the shared river as governed by continuing obligations that resist unilateral disruption. From the perspective of the community of interest principle, the dispute demonstrates the fragility of cooperative legal regimes when confronted with geopolitical conflict. Although the Treaty embodies the principle that shared watercourses generate reciprocal rights and continuing obligations, its effectiveness ultimately depends upon the willingness of both riparian states to accept that cooperation is a legal obligation rather than a matter of political discretion.
The Nile and the Grand Ethiopian Renaissance Dam
The Nile Basin lacks a comprehensive agreement binding all of its principal riparian states. This institutional fragmentation has been brought into sharp focus by the Grand Ethiopian Renaissance Dam, which Ethiopia inaugurated in September 2025 without reaching a comprehensive agreement with Egypt and Sudan on its filling and long-term operation.[8] Ethiopia asserts a sovereign right to develop hydropower within its territory; Egypt invokes historic reliance and warns of threats to its water security. Instruments such as the 2015 Declaration of Principles and a separate Cooperative Framework Agreement have proved to be inadequate to ensure joint management and cooperation over the shared watercourse.[9] From the perspective of the community of interest principle, the dispute illustrates the limitations of cooperative principles in the absence of a shared legal framework. While the Nile is an integrated international watercourse whose sustainable management requires coordinated decision-making, the absence of universally accepted institutional arrangements has enabled competing assertions of sovereign rights to prevail over the collective management of the basin.
The Mekong
The Mekong Basin illustrates a different limitation of the community of interest principle: the existence of an institutional framework that lacks the participation of all key riparian states. Although the 1995 Mekong Agreement established the Mekong River Commission to promote cooperation and equitable utilization, its membership is confined to the four lower-basin states, while China remains only a dialogue partner despite its upstream influence.[10] As a result, major upstream hydropower development continues largely outside the Commission’s legal framework, demonstrating that the effectiveness of the community of interest principle ultimately depends on the participation of all materially affected riparian states.
Legal Gaps
Three structural limitations continue to impede the practical realization of the community of interest principle.
- The principle suffers from a persistent enforcement deficit. Although the principle has been firmly established in judicial decisions, incorporated into the UN Watercourses Convention and the UNECE Water Convention, and widely recognized as reflecting customary international law, it remains weakly institutionalized in many river basins. Its effectiveness depends largely on the existence of permanent river basin organizations, regular mechanisms for information exchange and monitoring, and accessible procedures for dispute settlement. Where these institutional arrangements are absent, or where states refuse to participate in them or disregard their decisions, the principle offers few practical constraints on unilateral action.
- Significant doctrinal uncertainty continues to surround the relationship between the substantive principles of international water law. Neither the UN Watercourses Convention nor the UNECE Water Convention provides a definitive hierarchy or relationship between the principles of equitable and reasonable utilization and the obligation not to cause significant transboundary harm. As a result, upstream and downstream states frequently invoke different principles to justify competing legal positions, with upstream states generally emphasizing equitable utilization and downstream states relying on the no-harm rule. Although a growing body of scholarship argues that these principles should be interpreted harmoniously through the community of interest principle, the absence of clear treaty language continues to leave considerable room for conflicting interpretations and political manipulation.
- The principle remains vulnerable to the resurgence of unilateralism in contemporary international relations. The community of interest presupposes that states accept continuing legal obligations arising from the shared nature of an international watercourse. Yet recent state practice demonstrates that geopolitical rivalry, national security concerns, and domestic political priorities can quickly displace cooperative commitments. Where a state concludes that the political or economic benefits of acting alone outweigh the diplomatic or legal consequences, it may proceed with major infrastructure projects, reject the jurisdiction of international tribunals, suspend cooperative arrangements, or simply decline to participate in basin institutions. Unless the principle is supported by robust institutions, effective compliance mechanisms, and a stronger legal expectation of sustained cooperation, it will remain vulnerable whenever states perceive unilateral action to be politically or strategically advantageous.
Policy Recommendations
- Affirm the principle: Pakistan should consistently invoke the community of interest principle, alongside the principles of equitable and reasonable utilization and the obligation not to cause significant harm, as established norms of general international law in its diplomatic practice and multilateral engagement. Sustained and consistent reliance on these principles contributes to the development of state practice and opinio juris, reinforcing their status as settled rules of international law.
- Strengthen enforcement institutions: As the effectiveness of the community of interest principle depends on the institutional frameworks through which it is implemented, Pakistan should advocate for the strengthening of the Permanent Indus Commission (PIC). The goal should be to transform this institutional mechanism from an abstract legal principle into a framework of enforceable obligations.
- Resolve normative indeterminacy: Neither the Convention on the Law of the Non-Navigational Uses of International Watercourses (1997) (UN Watercourses Convention) nor the Convention on the Protection and Use of Transboundary Watercourses and International Lakes (1992) (UNECE Water Convention) explicitly defines the relationship between the principles of equitable and reasonable utilization and the obligation not to cause significant harm. This ambiguity leaves states with considerable discretion, creating opportunities for more powerful upstream states to advance interpretations that favour their interests. Pakistan should therefore support initiatives through the International Law Commission, United Nations forums, and model treaty development to clarify the interaction between these principles, as greater legal certainty would strengthen the position of downstream riparian states. Such efforts should also be guided by the community of interest principle, which reinforces the understanding that shared watercourses must be governed through cooperation, mutual restraint, and the protection of the collective interests of all riparian states.
- Ensure sustainable development of the shared watercourse: Pakistan should advocate for the application of the community of interest principle as the basis for integrated river basin management in international water law. Shared river basins should be governed as unified systems through basin-wide planning, joint management institutions, and coordinated environmental protection measures, rather than through fragmented, state-centric approaches.
[1] Territorial Jurisdiction of the International Commission of the River Oder (United Kingdom v Poland) (Judgment) PCIJ Rep Series A No 23, 27.
[2] Gabčíkovo-Nagymaros Project (Hungary/Slovakia) (Judgment) [1997] ICJ Rep 7, para 85.
[3] Lake Lanoux Arbitration (France v Spain) (1957) 12 RIAA 281.
[4] Convention on the Law of the Non-Navigational Uses of International Watercourses (adopted 21 May 1997, entered into force 17 August 2014) UNGA Res 51/229, arts 5–7.
[5] Convention on the Protection and Use of Transboundary Watercourses and International Lakes (adopted 17 March 1992, entered into force 6 October 1996) 1936 UNTS 269.
[6] Indus Waters Treaty 1960 (India–Pakistan) (signed 19 September 1960, entered into force 1 April 1960) 419 UNTS 125.
[7] Indus Waters Western Rivers Arbitration (Pakistan v India) (Award Concerning Maximum Pondage Supplemental to the Award on Issues of General Interpretation of the Indus Waters Treaty) PCA Case No 2023-01 (15 May 2026).
[8] Ahmed Morsy and Tsedenya Girmay, ‘With Ethiopia’s GERD Active, Tensions Mount Along the Nile’ (Middle East Council on Global Affairs, 25 September 2025) https://mecouncil.org/blog_posts/with-ethiopias-gerd-active-tensions-mount-along-the-nile/
[9] Agreement on Declaration of Principles between Egypt, Sudan and Ethiopia (signed 23 March 2015); Agreement on the Nile River Basin Cooperative Framework (opened for signature 14 May 2010), to which Egypt and Sudan are not parties.
[10] Agreement on the Cooperation for the Sustainable Development of the Mekong River Basin (signed 5 April 1995).
