Territorial disputes occupy an uneasy position within international dispute settlement. Traditionally resolved through diplomacy, power politics or even force, they are increasingly framed and addressed as legal claims. Although both purely political and judicial means of dispute settlement have become increasingly prevalent in territorial disputes, international arbitration has nevertheless long remained relatively under-utilised. It is often portrayed either as a weaker alternative to judicial settlement or as diplomacy clothed in legal language. However, by presenting arbitration as a distinct institutional form rather than a residual or derivative mechanism, Asaf Siniver effectively challenges this framing.

Siniver organised the book around a clear puzzle, outlined in Chapter 1. If arbitration combines consent with binding outcomes, why do States resort to it so selectively in territorial disputes, and why do they sometimes reject its results? Siniver’s answer is not that arbitration lacks authority. Instead, he notes that territorial disputes have long been approached either through diplomatic negotiation or judicial settlement, with adjudication commonly treated as the ideal legal method (2). Arbitration is therefore assessed by reference to standards derived from these models rather than examined on its own institutional terms. As a result, Siniver argues that the under-utilisation of arbitration is not caused by inherent deficiencies in arbitration itself, but by a fundamental misunderstanding and misapplication of its sui generis character as a hybrid method combining party autonomy with legal bindingness (7–8). This historical misunderstanding and the resulting misapplication are reflected in the judicialisation of arbitration, encouraged by the strong legalisation of arbitration within the European legal tradition (43), as well as in the over-regulation of arbitral procedure through instruments such as the Model Rules on International Commercial Arbitration (32).

To explain this persistent under-utilisation, Siniver’s analysis proceeds through a process-based framework. Arbitration is situated between mediation and adjudication, but not as an intermediate or subordinate form of dispute resolution. Siniver instead focuses on institutional design choices across the life cycle of a dispute. The framework separates the decision to pursue arbitration from the decision to comply with an award. It identifies recurring mechanisms, including domestic political cover, reputational considerations and legally framed objections grounded in jurisdiction or justiciability (Chapter 3). These mechanisms are traced through procedural choices and post-award behaviour rather than inferred solely from award texts. The four case studies—Rann of Kutch (Chapter 4), Beagle Channel (Chapter 5), Taba (Chapter 6) and the South China Sea (Chapter 7)—follow a consistent structure. Each examines the political context, the design of the arbitral process and the post-award phase. The award itself is not treated as the analytical endpoint.

At the core of this framework lies a claim about hybridity. Siniver argues that arbitration’s distinctive value lies in the combination of procedural autonomy, flexibility and legal bindingness. By means of this structure, States can tailor the dispute settlement process to their specific needs and secure a final, enforceable resolution. He notes that the prevalent view of arbitration as both inferior to adjudication and excessively restrictive for State autonomy misses what he describes as its greatest institutional advantage (2): that arbitration allows States to retain significant control over process design while still obtaining a final, legally binding and equitable outcome (2–3). This hybrid design can recalibrate the relationship between legitimacy and effectiveness in territorial disputes, while leaving room for contestation once the award is rendered. Courts function as an implicit point of comparison throughout the book, particularly in discussions of jurisdiction and institutional authority.

The four case studies clearly illustrate both the promise and the fragility of the hybrid institutional design of international arbitration. In the Rann of Kutch and Taba, arbitration facilitated outcomes that would have been difficult to achieve through other means. Party autonomy at the design stage played a stabilising role and supported domestic acceptance of the result. In the Beagle Channel and the South China Sea, the same flexibility proved destabilising. Entry into arbitration and participation in the process remained sufficiently discretionary to allow post-award rejection to be framed as legally defensible, especially through jurisdictional and justiciability arguments.

One implication of this account nevertheless warrants further reflection. As introduced above, Siniver treats misunderstanding of arbitration’s sui generis character as a factor contributing to the lack of recourse to arbitration. He persuasively explains this misunderstanding of arbitration’s nature as a hybrid method of dispute settlement, tracing its historical origins in the judicialisation and over-regulation of arbitration. Yet this so-called ‘misunderstanding’ can also function as a political tool in the practice of arbitration. Governments can present arbitration externally as a neutral legal process when they succeed, while invoking it domestically as an outcome imposed by an external authority when they fail. In this setting, such dynamics can help to stabilise political accommodation by framing it as a legal necessity. At the same time, the political elements embedded in arbitration can weaken the authority of the legal relief it produces. Therefore, arbitration inevitably faces a paradox arising from its hybrid nature. While clarifying misunderstandings about this hybridity might encourage greater recourse to arbitration, increased use may also lead to greater instrumentalisation of its hybrid character. Does an increase in the use of arbitration necessarily lead to a more appropriate use of its hybrid nature and to greater effectiveness? This remains to be seen.

Overall, Siniver succeeds in repositioning arbitration within international dispute settlement as a distinct institutional choice. He shifts attention away from outcomes and towards arbitration as a process shaped by consent, design and post-award practice. By placing hybridity at the centre of the analysis, Siniver explains both why arbitration remains attractive to States and why it is often fragile in practice. For scholars and practitioners confronting territorial disputes where adjudication is unavailable, Siniver’s analysis clarifies both what arbitration can deliver and where its limits lie.