This article interrogates the misunderstanding about the inability of legal rules to influence relations between states in transboundary river basins. Building on the interactional theory of law, the author formulates three analytical frameworks for understanding the role of legal rules in the processes of cooperation and peaceful settlement of disputes in transboundary river basins. The article ultimately argues that law offers broader utility than previously envisaged to these processes. In conclusion, it teases out five such utilities of legal rules as demonstrated by four case studies in a broader study.

  • The claim that law cannot affect relations between states, especially in the context of their transboundary rivers, is unfounded.

  • Interactional theory of law provides a prism for better understanding the utility of legal rules in general.

  • In this case, the theory tests and provides the broader utility of legal rules in the processes of cooperation and peaceful settlement of disputes in transboundary river basins.

There are over 310 transboundary rivers and lakes and around 510 transboundary aquifers worldwide (McCracken & Wolf, 2019). These basins are shared by 150 countries and disputed areas, covering 47.1% of the Earth's land surface (without Antarctica), including 52% of the world's population (United Nations World Water Development Report, 2014), and account for approximately 60% of the global river flow (United Nations Annual Report, 2008). A substantial part of the shared freshwater resources forms a part of areas where water and security are intrinsically linked. Furthermore, many shared rivers, like the Nile, Indus, Mekong, and Jordan Rivers, are characterized by substantial interstate and intrastate armed conflicts (Priscoli & Wolf, 2009; Allan & Mirumachi, 2010). Climate change has a multiplying effect on the challenges of these resources (Parry et al., 2007; Sanchez & Roberts, 2014; Ruttinger et al., 2015).

Hence, many disputes have arisen within the context of shared water basins. At the same time, contemporary disputes over shared water resources have now gone beyond the traditional water quantity (allocation and access), international boundary, and navigational issues to encompass water quality, right of use, human rights to water and sanitation, energy production, water pollution, and water trade or virtual trade or bulk water trade. Moreover, such disputes now involve several parties, including non-state actors like corporations, individuals, civil societies, and international organizations. They are also often inseparable from the broader interstate tensions from which they may arise (Boisson de Chazournes, 2015).

States usually rely on legal rules while engaging in dispute settlement procedures/mechanisms, including peaceful settlement and adversarial means to settle their transboundary water disputes. Based on the nature of such disputes and state practice, peaceful settlement procedures offer the best practical option (Caflisch, 2003). These procedures are flexible to accommodate the evolving nature of international water law, such as the evaluation of technical water data; they also allow parties to be in charge of the process, provide for balance to power asymmetry between the parties, and often lead to equitable solutions.

There are situations where riparian states have relied on legal rules and engaged with peaceful settlement procedures, which have resulted in the conclusion of agreements; nevertheless, they have been unable to resolve their transboundary water disputes effectively. In such situations, many are ready to cast their failure on legal rules. This conclusion has led to doubt about the utility of legal rules in international planes, particularly in international water law. Hence, the fundamental inquiry in this article is: What are the roles of legal rules in the cooperation and peaceful settlement of disputes in transboundary river basins?

This article utilizes an interactional theory of international law to address the research question above. The method helps interrogate the narrow conceptualization of legal rules' role in cooperation and peaceful settlement of disputes in transboundary river basins. It will help investigate and provide a broader understanding of the role of legal rules in those processes. It will also tease out and explain factors that contribute to a more comprehensive understanding of the role of law in those processes.

This article, in Section 1, starts with setting the context of shared freshwater resources. It discusses various freshwater challenges that influence various water disputes. It also discusses the preferences of the state to settle their transboundary water dispute via peaceful settlement because of the unique features of the processes and such disputes. It further discusses the misunderstanding of the scholars on the roles of legal rules on cooperation and peaceful settlement of transboundary river disputes. It introduces the research question and the research method.

The next section of the article, Section 2, will briefly discuss the contours of the legal rules of cooperation and peaceful settlement of disputes. Analysis in the section will concentrate on the development of the two global agreements of transboundary freshwater resources, which provides for the core principles and legal rules for cooperation and peaceful settlement of disputes in transboundary rivers. It will also discuss the implications of the application of the parallel agreements. To highlight its niche and situate the research in its proper context, Section 3 of this article will briefly review the relevant literature on interdisciplinarity in transboundary water research. The analysis will focus on interdisciplinarity between international law and international relations.

The remaining section introduces and discusses the contour of the methodological approach of this article. Section 4 will introduce the interaction theory of law in transboundary water research. Section 5 will discuss the differentiation between the original application of the method and the reformulated version of the method. It stretches out the places of agreement and disagreement with the original formulation and application of the original method. It also explains the reasons and arguments for its disagreement. With the reformulated method, Section 6 will introduce its three analytical frameworks for analysis: the effect of norm processes, the effects of water-related arrangements and/or agreements, and the effect of international water law.

Over the years, the wide variety of international water agreements resulted in considerable incongruity in the rules of transboundary freshwater management, especially where legal principles were devised or interpreted to fit specific state interests (Eckstein, 2020). As a result, various (and often incompatible) legal concepts emerged regarding allocating and sharing transboundary waters. These notions and modes of state practice varied from one self-centred perspective of absolute territorial sovereignty and absolute territorial integrity to the more balanced and equitable viewpoint of limited territorial sovereignty, including the more holistic community of interest approach (McCaffrey, 2019).

In 1954, the International Law Association (ILA) instigated the initial effort to bring uniformity and consistency to transboundary water management by exploring the topic of ‘inland water rights and obligations of States’ at its Edinburgh Conference (Bogdanovic, 2019). After a decade of debate, ILA produced its highly influential rules for transboundary drainage basins, the Helsinki Rules on the Uses of the Waters of International Rivers (1966 Helsinki Rules), which is most notable for its rules on equitable utilizations. Over the years, some of the Helsinki Rules have been used and are still used as a basis for negotiations in transboundary water arrangements.

In 1996, the ILA adopted the Berlin Rules with the aim of integrating all international legal rules regarding water resources into a single set of rules (Dellapena & Gupta, 2008). An updated version of the Berlin Rules was adopted in 2004. The 2004 Berlin Rules are comprehensive, covering all freshwater and related resources (the aquatic environment), and integrating domestic and international water law. The Berlin Rules also involve the first comprehensive attempt to address the distinct characteristics of groundwater (Dellapena & Gupta, 2008). As the most recent articulation of legal rules on transboundary river management, it takes into account the latest developments in international water law including the modern principles of international water law and robust provisions on mechanisms for peaceful settlement of disputes (Dellapenna, 2006). Despite their pioneering and progressive influences, both the Berlin and Helsinki Rules are recognized only as unofficial and informal articulations of the international water rules.

The initial concrete effort towards adopting a formal universal legal instrument on international water governance commenced with the United Nations General Assembly's recommendation to study the law of the non-navigational uses of international watercourses with a view to its progressive development and codification in 1970. The International Law Commission (ILC) took the recommendation and began working on the topic in 1974. The work of the ILC in this regard was built on studies of the Institute of International Law (IIL) and the ILA. After over 25 years, the ILC produced the draft articles, which were later negotiated and adopted at the United Nations General Assembly as the UN Convention on the Law of the Non-Navigational Uses of International Watercourses (UN Watercourses Convention) (McCaffrey & Sinjela, 1998). The Convention only entered into force in 2014.

The second global water convention started under the United Nations Economic Commission of Europe (UNECE)'s work on water services in the 1940s, within the mandate of its Committee on Electric Power, established in 1947 (Berthelot & Rayment, 2007). After years of negotiations, the UNECE Convention on the Protection and Use of Transboundary Watercourses and International Lakes was adopted in 1992 (UNECE Water Convention). It entered into force in 1996. Although the convention was initially conceived as a regional instrument, it was later amended and open to all UN member states (Trombitcaia & Koeppel, 2015). The procedure for amendment of the agreement was adopted in 2003. Ten years later, in 2013, the necessary ratifications were reached, and the amendment was announced to enter into force in 2016 (Fitzmaurice & Merkouris, 2015).

Consequently, there are two universal formal instruments on transboundary water governance. Both instruments, especially the Watercourses Convention due to its codification process, are referred to as the articulation of customary rules of transboundary water management. Notwithstanding, both agreements have had limited ratification by states. For the Watercourses Convention, there are 38 ratifications. On the other hand, the Water Convention has 52 ratifications including over 11 non-European states. This limited ratification of the agreements may call into doubt the customary nature of the provision of these agreements. Although international courts have pronounced the customary nature of some rules of international law codified in the conventions (Tignino & Brethaut, 2020), the recent decision of the court in Silas vs Bolivia failed to make such an analysis (Dellapenna, 2023).

Ultimately, the coexistence of the two instruments not only gives rise to the question of how the provisions of the two conventions overlap or differ but also gives rise to the question of what the legal implications for a party are joining the two agreements. After a comprehensive review of the relevant provisions of the treaty agreements and the two universal water agreements, it is concluded that the two water conventions are essentially compatible with one another (McCaffrey, 2015; Lammers, 2018). The compatibility of the two agreements seems inevitable because the agreements were negotiated in the same period, and there was a cross-fertilization of ideas between the drafters/negotiators of the two agreements.

The two agreements provide, to varying extents, the three core principles of international water law: equitable utilization, the prevention of significant harm, and cooperation. Under the principle of prevention of significant harm, the Water Convention provides a more comprehensive scope of transboundary harm (Art. 1(2)). On the other hand, the Watercourse Convention provided a qualification ‘significant’ as a threshold for harm (Art. 7(1)). The Watercourses Convention also contains a more detailed provision on the principle of equitable utilization (Art. 5(1)). Both conventions provided for sets of procedural rules under the principle of cooperation. These procedural requirements include rules of notification (exchange of information), protection of the environment, and peaceful settlement of disputes. The Water Convention mandates the creation of water bodies as a cooperative mechanism, among other roles of such bodies. In this regard, it creates the Water Secretariat, the Meeting of Parties, and other technical bodies (Art. 9(2)). On the other hand, the Watercourse only prescribes their creation (Art. 8(2)).

The synergic application of the principles provides a robust framework for the cooperation and peaceful settlement of disputes in the transboundary river basins. For instance, the principle of prevention of significant harm provides for states to always give ‘due regard’ to the principle of equitable utilization whenever ‘significant harm’ occurs. On the other hand, the principle of equitable utilization considers the extent of ‘transboundary harm’ as one of the factors in determining equitable and reasonable uses. At the same time, the effective implementation of the two substantive principles is guaranteed through procedural requirements of the principle of cooperation (McIntyre, 2017).

On the peaceful settlement procedures as part of the cooperation principles of international water law, the Watercourses Convention recalled the broad spectrum of diplomatic mechanisms and procedures for the peaceful settlement of international water disputes, including the compulsory fact-finding procedure (Tanzi & Milano, 2013). The UNECE Water Convention, on the other hand, contains succinct provisions on dispute settlement. It provides that ‘parties shall seek a solution by negotiation or any other means of dispute settlement acceptable to the Parties to the dispute’ (Art. 22 (1)). However, the fact that the UNECE Water Convention does not mention the diplomatic procedures should be read within the background of its provision enshrining the obligation to establish joint bodies that provide a platform for a range of dispute prevention and resolution procedures (Tanzi, 2001; Tanzi & Contartese, 2015). Such practice of transboundary water cooperation through an institutional framework is a particularly distinguishing feature of international water law (Boisson de Chazournes, 2003; Leb, 2013).

Our study here is focused on interdisciplinarity between international law and international relations. Historically, practitioners in both fields have pursued common interests for several decades before the Second World War. The war, however, served as a watershed event as the realist International Relations (IR) scholars rejected the notion that international law could be a meaningful constraint on states' pursuit of their national interests (Dunoff & Pollack, 2013). Over the next four decades, IR and International Law (IL) scholarships developed along separate and rarely intersecting tracks. The mutual neglect between the two disciplines began to fade only towards the end of the Cold War and the resultant effect of the proliferation of international rules and institutions.

Towards the end of the Cold War and the period afterwards, some scholars called for interdisciplinary research between the two disciplines (Abbot, 1989). Despite the development, only a few scholars have heeded the call (Young, 1989; Slaughter, 1993; for other relevant IR/IL scholarships, see, Kratochwil, 1989; Onuf, 1989; Slaughter et al., 1998; Arend, 1999; Byers, 1999; Toope, 2001). Most scholars from both fields have continued to work in isolation, even on issues where both disciplines possess a mutual interest, like normativity: ‘International lawyers continue to invent norms and institutions, rarely questioning the effectiveness of their creation; while international relations scholars continue to describe the evolution of norms, rarely attempting to differentiate between norms that are binding or merely influential, or to ask whether a difference between categories of the norm is relevant' (Toope & Brunnee, 1998).

IL/IR interdisciplinarity can help scholars, international lawyers, and norm-interested IR scholars work together by learning from each other to understand the norms’ instrumentality better. In this regard, IL scholars can learn how international law functions in the society from IR scholars. For instance, the latter can explain how legal rules can broadly be congruent with the practices in the society or how they evolve from a shared understanding to be effective. On the other hand, IR scholars would learn from IL scholars how the legal norms shape and influence the conduct of international actors. This is important because IR scholars tend to look at international law through the prism of the domestic legal system, whereas the international order including international law is horizontal in structure without legislative and executive hierarchy as in the domestic system. Hence, the blend of insights from both disciplines provides a broader understanding of legal rules in the international society (Brunnee & Toope, 2010).

With few exceptions, IL/IR interdisciplinarity is rarely pursued in the context of shared freshwater resources. One of the works in this area includes Benvenisti's study, ‘Collective Action in the Utilization of Shared Freshwater: The Challenges of International Water Resources Law’, which diagnoses freshwater resources management as a collective action problem, drawing on the IR literature to specify the principles for overcoming collective actions problems. It then evaluates alternative procedural and substantive options for regulating water resources management at the international level in the light of these principles (Benvenisti, 1996).

Another noticeable exception is the work of Zeitoun et al. Focusing on the limited existing transboundary water arrangements in their article, they advocate for critical evaluation of the processes that establish and maintain transboundary water arrangements through an interdisciplinary method of ‘transformation analysis’ to render a more suitable and equitable transboundary water arrangement (Zeitoun et al., 2019). The author also highlights the need for further research in transboundary water conflict research if one would significantly affect practice.

In promoting environmental security in shared freshwater resources, Toope and Brunnee's work draws together insights from regime theory from international relations and international law (Brunnee & Toope, 1997). Their approach, interdisciplinary regime theory, helps explain how binding legal norms may emerge from patterns of expectations developed along a non-linear continuum of coordinated dialogue and actions in a particular issue area, such as shared water regimes. They, therefore, argue that shared freshwater regimes built on value-associated norms with ecosystem-oriented concepts like sustainability, intergenerational equity, precaution, and a common concern are the most likely to fulfil the regimes' environmental security paradigm.

In their subsequent work (Toope & Brunnee, 1998), the authors assessed the application of their interdisciplinary regime theory in shared waters to the mandate of the International Joint Commission (IJC) as a sui generis institution. IJC appears to contradict interdisciplinary theory since the theory seems to mandate the need for regimes to evolve before specific norms can emerge to create strong institutions. However, the evolution and operations of IJC show that it conforms to the principles of theory, including the interplay between relevant international norms. Moreover, its operations and influence have continued to contend with the interest of relevant actors like the member states. Despite the IJC's attempts to break out of the narrowness of its constituting legal framework, it has been curtailed by increasingly reluctant state parties (Chandler & Vechsler, 1992; Lemarquand, 1993). Hence, the experiment shows that the interdisciplinary regime theory can still apply to existing institutions.

International law and its rules, for a long time, have continued to be misrepresented by certain sections of scholars. For instance, the rationalist IR theory attributes the law to a limited role in influencing states' behaviour. Most IR scholars also only construe a formalistic and positivist conception of law. Positivist legal scholars also support this view. Such perspectives have continued limiting the influence, understanding, or contribution of international rules. In reality, international legal rules perform quite broad roles, hence the need to address these misconceptions.

The interdisciplinary work of Brunnee and Toope, among other things, provides an excellent framework for analysis of the roles of international legal rules from a broader perspective (Brunnee & Toope 2002a, 2002b, 2010, 2011, 2018, 2017). Their work, interactional theory of international law, connects insights from the IR constructivism (for relevant works on constructivism, see Onuf 1982, 1985, 1998; Kratochwil, 1984a, 1984b, 2000; Finnemore & Sikkink, 1998; Ruggie, 1998) and practice theory to the legal theory of Fuller (1969). Their approach understands law not as a hierarchical ordering but as an ongoing generative activity oriented towards constructing relatively stable patterns of practices and normative expectations. The approach opens new vistas on the roles of international law as neither imposes social control; instead, they are seen as generated and moulded through interaction. Accordingly, the law is seen as an ‘enterprise and a social practice – a continuing challenge rather than a finished product and allows for the influence of emerging norms even when they have not yet attained legal status’.

The approach also distinguishes legal norms from other types of social ordering. Such characteristics of legal rules include generality, promulgation, non-retroactivity, clarity, compatibility, constancy, non-contradiction, not asking for the impossible, and congruency between laws and official action (Fuller, 1969). These internal legality features are crucial to generating distinctiveness, legal legitimacy, and adherence or compliance. Hence, the approach argues that legal rules, as part of the contributory factors to influencing the state's action or inaction, have independent explanatory and normative forces that are distinguishable from other social norms.

From the perspective of international law, the approach recognizes the horizontal (and not hierarchical) nature of law, which aligns with the international law system and its core ‘duty of reciprocity’ (Brunnee & Toope, 2010). It also liberates international law from the distorting optic of the ‘monopoly on power’ and ‘enforcement’ fixations, making positivist lawyers and some IR experts discard the utility of international law. It opens up law-making to a diversity of participants beyond the sphere of states to include non-state actors actively engaged in the creation of shared understandings within the international community. Moreover, it allows for multiple spheres of the impact of legal rules, both by accounting for the normative influence of states and non-state actors and by opening up the notion of ‘sources’ of international law.

This study provides an opportunity to apply the ‘interactional theory of international law’ and assess the role of legal rules in cooperation and the peaceful settlement of disputes in transboundary river basins. It permits the development of analytical frameworks of analysis for a holistic analysis of the role of law in those processes. Through the frameworks, it will explain how the evolving legal rules on shared freshwater help define or redefine stakeholders’ actions in the shared river basins towards cooperative or competitive behaviours.

The original formulation of the theory has been applied by its proponents in their analysis of the role of law in the Nile Basin Regime (Brunnee & Toope, 2002a, 2002b). Their work analyzes the role of law in shaping the interactions among the Nile basin states from the nineteenth-century institutions and arrangements to the newly created institutions, such as the Nile Basin Initiative (NBI). Restating the difference between the interactional theory and the formalist or positivist theorists, the authors stated that ‘if one's expectation of law is that by its mere formal existence (as an enunciated ‘rule’) it can directly cause behaviour, then one would inevitably conclude that international water law has been ineffective in the Nile context’.

However, the authors’ application of the interactional theory provides a nuanced and broader understanding of the law. They conclude that throughout the meandering evolution of the Nile Basin regime, legal norms have been influential and have both hindered and promoted cooperation. They further conclude that the evolving normative framework for shared freshwater has helped redefine the behaviours and interests of key actors in the Nile River basin while moving them into more cooperative behaviours. Their analysis is, however, structured around three conceptual frameworks: the effect of the Historical Treaties, Informal interaction among the Basin States, and the Effect of International Water Law.

The authors make somewhat contradictory arguments in the third analytical framework of the ‘effect of international water law’ compared to the above general conclusions. Concerning the framework, they argue that the framework of international water law has ‘reinforced separate, competitive identities’ between riparians. It has also ‘served to reinforce self-interested and ultimately unconvincing legal arguments’. Furthermore, it argued that the Watercourse Convention ‘perpetuate the competitive paradigm’ and its terms ‘may promote the maintenance, or even the reinforcement, of the separate identities of riparians’.

This study disagrees with the above conclusions, and instead, it argues and demonstrates that legal rules of contemporary international water law offer sufficiently developed alternative conceptual frameworks that could facilitate cooperation and peaceful settlement of disputes in transboundary river basins. As highlighted in the previous section, the fundamental approach of the international water law is rooted in its core principles and the underlying idea of mutual limitation of sovereignty rights. The core principle includes the principles of no significant harm, equitable utilization, and cooperation. The limited sovereignty approach dictates that a state's right to use its territory is limited by the duty not to cause significant harm to another state (Watercourse Convention, Art. 7).

When significant harm occurs or is expected to occur, it is ultimately resolved by balancing interests under the equitable utilization framework. What is equitable is determined in each case and depends on factors ranging from geography to economic, social, and demography (Watercourse Convention, Art. 6). This result, in turn, is tempered by the requirement that the state causing harm consults or cooperates with the affected state ‘to eliminate or mitigate such harm, and where appropriate, discuss the question of compensation’ (Watercourse Convention Art. 7). Other provisions of the convention provide for a robust cooperative framework of procedural rules (Watercourse Convention, Arts. 8, 9, 11, 12, 15–18, and 24). Hence, a synergic application of both frameworks – equitable utilization and cooperative frameworks – provides open-minded and substantial guidance for robust dialogue necessary for the emergence of shared understanding between parties on relevant issues.

Several transboundary river basins are experiencing changes, including the Nile River basin, since the assessments of the authors. Some of these changes flow from the recent development of the global frameworks on transboundary freshwater rules. On the other hand, some of the changes result from specific contextual realities within the basins. This study provides an opportunity to reassess the role of law in the basin while taking into account these developments. It provides further opportunity to an expanded application of the reformulated theoretical and analytical frameworks beyond the Nile River basin to other transboundary basins like the Mekong River, the Jordan River, and the Indus River (Edum, 2024). The approach will prove the robustness and credibility of the interactional theory of law and its analytical frameworks.

The most controversial hypothesis for the theoretical approach is that the evolving legal norm influences changes in international planes, ‘but not through the creation of predictable rules and institutional structures’ as positivist international lawyers and rationalist international relation scholars postulate (Brunnee & Toope, 2000). The approach frees one from the narrow and restrictive characterization of international law (Krasner, 1983; Abbot et al., 2000). Such a liberating understanding of the role of legal rules would lead to recognizing the full range of contributions of legal norms in cooperation and peaceful settlement of the transboundary river basin. In this regard, the study provides three analytic frameworks for its analysis: the norm-generating process, the effect of water-related arrangements in the basin, and the effects of international water law.

Norm-generating processes

This framework discusses the process-based approach to cooperation and peaceful settlement of disputes in transboundary river basins. Analysis based on the effect of norm-generating processes is fundamental to understanding the role of law, without which the role of law is seen as only coming at the end of a process to formalize the agreed outcome and render it ‘binding’ (Brunnee & Toope, 2010). The analysis of the case studies under this framework emphasizes that a ‘final’ legal framework already emerges in the patterns of interaction among the riparian states. These patterns gradually reshape the basin state's identities, shift the parameters of persuasive arguments that might be viewed as the emergence of a ‘water rhetoric’, and, crucially, promote enhanced legitimacy for the evolution and consolidation of legal norms.

The composition of participants in the norm-generating process is also essential. The process may bring together water experts from within or outside the basin, that is, epistemic communities (Haas, 1989). Participants can also be drawn from government ministries; in this case, it is described as ‘intergovernmental networks’ (Slaughter, 2001). The networks can play an essential role in transferring expertise and knowledge. However, they can also be hijacked by the dominant player for the promotion of normative goals and not necessarily the collective interests of the parties (for research on norm entrepreneurship, see Keck & Sikonk, 1998). Third-party parties, like international organizations or other states, can play a significant role in regime development and peaceful settlement of international water disputes if they can exercise their role with sensitivity to states’ concerns and commitment to the evolution of norms between the disputing parties or riparian states (Dinar, 2000).

Effect of water-related arrangements and/or agreements in the basin

The interactional theory of international law informs that it is crucial not to mistake the formal representation of law for successful law-making (Brunnee & Toope, 2010). Although formal indicators like treaties provide useful indicia of the existence of binding rules, purely formal terms offer limited guidance in analyzing how obligation is created in the international society. Interactional international law argues that soft norms may sometimes possess more obligatory force than norms derived from formal sources like treaties (for research on soft laws, see Weil, 1983; Chinkin, 1989; Dupuy, 1991; Klabbers, 1996). Hence, the theory and its approach make sense of the most critical ways international law is made in contemporary practice: custom, treaty, and soft law.

Since arrangements (including the hard and soft laws) provide for norms, analyzing the water-related agreements in transboundary river basins starts with understanding the norms’ capacity to inhibit or facilitate the emergence of dynamics or a collective identity formation of states. These norms can promote the construction of collective identities and collective definition of interests by framing processes that foster mutual understanding. Along the same line, norms can articulate ‘categories’; that is, they can contribute to the formation of hardening of separate, competitive identities (Kowett, 1998; Glenn, 2000).

Effect of international water law

This framework aims to test the effect of the regime of international water law in the regime development and peaceful settlement of disputes in the selected transboundary river basins. It is, therefore, an extension of the application of the principles of the interactional theory of international law in the regime of international water law. The analysis in this regard starts with the acknowledgement that international water law derives from the international law principle of sovereignty. As such, one of the great theoretical dilemmas of international water law was how to reconcile the sovereignty of states over their territory with their obligations under international law vis-à-vis other states with which they share freshwater resources. Over time, there have been theories and concepts to represent such relationships, namely, the principle of absolute sovereignty, limited sovereignty, and the concept of community of interest.

However, the current discourse of international water law is focused on three broad principles: prevention of harm, equitable and reasonable utilization, and cooperation. The first two principles are understood as creating substantive obligations. On the other hand, the third principle is commonly understood as a composite obligation comprising a comprehensive set of procedural requirements for achieving the substantive principles. This procedural obligation includes exchanging information, consulting and negotiating in good faith, and ensuring the peaceful settlement of disputes. International water law, or at least the two global transboundary water conventions, which are framework agreements, have left states to define the extent of these procedural requirements.

This article interrogates the misunderstanding of scholars on the roles of legal rules in cooperation and peaceful settlement of transboundary river disputes through the application of the interactional theory of international law. It briefly discusses the contour of the legal rules of cooperation and peaceful settlement of disputes in the field. It also briefly analyses the relevant mythological framework of transboundary water research. After that, it discusses the contour of the interactional theory of international law. Building on the theory, it introduces its three analytical frameworks for analysis: the effect of norm processes, the effects of water-related arrangements and/or agreements, and the effect of international water law.

Application of the methodological approach and its analytical frameworks on four case studies in a broader study provides for the holistic role of law in the cooperation and peaceful settlement of disputes in transboundary river basins (Edum, 2024). This study also illustrates five fundamental roles of the legal rules in those processes. First, legal rules interact with other norms, like economics or politics, in defining and influencing relations between parties in the basin. Second, the law's role is neither confined to formalizing agreements previously reached through purely strategic bargaining nor to establishing explicit entitlements. Third, legal rules (whether provided in soft or hard arrangements) must fulfil a legality test to be able to generate adherence. Fourth, legal rules are effective in guiding what counts as persecutive arguments for acceptable behaviour/actions. Fifth, legal rules can also play a double-edge effect of hindering or facilitating cooperation.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.

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