Wolfgang Alschner's monograph Investment Arbitration and State-Driven Reform has an ambitious agenda when assessing the state of investment law: showing us ‘how we got here, what is wrong with where we are, and what we can do about it’ (xviii). In his answers to these questions, Alschner has provided a profoundly stimulating contribution to the debate on the development and reform of investment law that combines empirical scholarship with doctrinal analysis and normative proposals. His key argument is that the distinction between ‘classic’ and ‘modern’ bilateral investment treaties (BITs) has not mattered much in practice. Instead, tribunals continue to interpret modern BITs—which frequently contain clarifications, specifications and exceptions that were supposed to push investment law in a direction more amenable to State interests—in the same way as ‘minimalist’ treaties. Uncovering this dissonance and charting ways in which the application of investment treaties by tribunals can be aligned with States’ reform agenda form the heart of this work.

Alschner opens with the most innovative part of the book, when he turns to data science to derive an understanding of broader trends from the thousands of diverse investment agreements (Chapter 1). This analysis is based on the Electronic Database of Investment Treaties (EDIT), a searchable, full-text, open-access database of investment agreements covering 99.75% of investment treaties in force, developed at the World Trade Institute, Bern. Using natural language processing, Alschner arranges the treaties according to their variance, using as a yardstick the frequency by which words occur in the treaty texts (33–4). In this way, he lets the ‘treaties speak for themselves’ (31) and maps the macro changes in investment treaty-making. He visualizes these changes in tables that demonstrate how treaties have become more sophisticated over time, as States have increasingly included clarifications, specifications and exceptions (eg general exceptions or national security exceptions). For Alschner, this development should be best understood through the lens of contract theory and constitutes a quest to achieve more ‘complete’ treaties (Chapter 2). The path towards more ‘complete’ treaties, he claims, has been defined by innovations in treaty-making emanating from the United States and Canada over the past decades (Chapter 3). On the basis of these changes in treaty-making, he offers a re-evaluation of States as a ‘reactionary’ force in the investment law universe. The field, he claims, has always been shaped by the titular variety of State-driven reform.

The aims of such State-driven treaty reform—to achieve a better balance between flexibility and rigidity, and re-balance interpretations by early investment tribunals—have, however, largely been frustrated according to Alschner. He sees the reason for this in three ‘normative devices’ (46) that gave rise to the persisting influence of old investment treaties on the decisions of arbitral tribunals, and he dedicates a chapter to each of them: most-favoured nation (MFN) clauses (Chapter 4); the use of customary international law (Chapter 5); and the force of precedent (Chapter 6). Chapter 6, in particular, makes a compelling case to explain the ‘stickiness’ of precedents based on old treaties that stifle the effect of treaty reform (eg 198). In addition to their evaluation of the doctrines, the last sections of Chapters 3–5 also contain proposals concerning how tribunals should ‘correctly’ interpret certain investment treaty provisions. Owing to their limited scope, these parts do not always reach the depth of analysis with which other parts of his book can impress the reader.

Some aspects of Alschner's assessment of customary international law in Chapter 5 could also have benefited from further clarification. He criticizes how tribunals have employed customary international law to gloss over differences between treaties. One key problem he identifies is that States have used references to custom as a tool to ‘write more contractually complete and balanced’ investment agreements (153). Many tribunals, however, have ignored these references or interpreted the customary minimum standard dynamically by reference to the evolution of investment law (156–7). This, for Alschner, is a means to counteract reform. Yet, one has to take into account that a reference to custom with its notoriously slippery nature seems to be ill-suited to clarify or lock in the substance of treaty provisions.

In its final Part III, the book seeks to map ways forward. Chapter 7 relies on the classic methods of treaty interpretation but combines them with insights from contract theory, to insist on a ‘forward looking’ interpretation of existing investment agreements in the light of recent reform efforts. Such interpretations are, however, not supposed to be a substitute for the renegotiation of outdated treaties, addressed in Chapter 8. Here, Alschner offers an illuminating hands-on perspective for government lawyers facing the question of how to implement treaty reform. His proposals for negotiators are actionable and clear: renegotiate treaties that matter based on the covered foreign direct investment flows and their normative impact in terms of maximum treaty overlap and minimum litigation risk (252: ‘few treaties matter a lot, and most treaties matter little’). Finally, Alschner points to the reform of international tax treaties through the Multilateral Instrument as a potential way forward for investment law (Chapter 9).

The style of the book is accessible, engaging, and at times creative in the best meaning of the word. He compares the messiness that negotiators face with dozens of BITs being simultaneously ripe for renegotiation to the feeling of a dinner party clean-up (252: ‘[w]here even to begin?’). When he likens investment treaties to an armada of ships that can only travel as fast as the slowest boat (11), one can almost see the 3000-something investment agreements traverse the world's oceans. In addition, he complements his writing with many graphs and tables. While most of the figures employed underline arguments of the text, others are difficult to decipher (eg 150, 196).

This monograph will be most useful for academics who want to sharpen their understanding of investment treaty practice and government officials who seek to add to their toolbox. With his book, Alschner has written a major contribution to the evolving debate on investment treaty reform. He meaningfully combines data science, doctrinal analysis and policy recommendations to dissect what he considers foundational shortcomings of investment law and constructively charts ways forward. For anyone interested in the future of international investment law there is no way around this book.