There could not have been a better demonstration of the timeliness of Daniel H Joyner's and Marco Roscini's book than the political events of March 2014. The cover image of this edited volume, entitled Non-Proliferation Law as a Special Regime, shows former President Dmitry Medvedev and US President Barack Obama as they sign the 2010 Strategic Arms Reduction Treaty, better known as ‘New START’. Less than four years later, the Crimea conflict led observers to question the remaining legal value of the New START regime. Had politics, somehow, rewritten the States parties' legal obligations?

To remain functional, non-proliferation law must be sensitive to its political ecosystem—by encouraging compliance with primary rules for limiting armaments but also by defining suspension and exit options when compliance becomes politically unacceptable. It is thus intuitive to expect that the secondary rules of non-proliferation law—rules ‘for the conservation or for the transformation of the primary rules’ (Bobbio)—would have special characteristics. The aim of this book is to explore the degree to which non-proliferation law is a ‘special regime containing specific secondary rules and principles that differ from rules of general international law and [from] those of other special regimes’ (10).

Following an enlightening conceptual introduction by the editors, the book's eight substantive chapters examine various ways in which non-proliferation law may differ from the more general practice of the law of treaties (Part I) and the law of State responsibility (Part II). Using a framework of analysis defined for all chapters by the editors, 11 authors present a competent analysis of the following areas: Amendment and modification of non-proliferation treaties (Malgosia Fitzmaurice and Panos Merkouris); Provisional application of non-proliferation treaties (Andrew Michie); Interpretation of non-proliferation treaties (Nigel White); Violation of non-proliferation treaties and related verification treaties (Eric Myjer and Jonathan Herbach); Withdrawal from non-proliferation treaties (Daniel H Joyner and Marco Roscini); The ‘injured State’ in case of breach of a non-proliferation treaty and the legal consequences of such a breach (Matthew Happold); Non-proliferation law and countermeasures (Sahib Sing); State responsibility consequences of termination of or withdrawal from non-proliferation treaties (Dieter Fleck).

Fitzmaurice and Merkouris identify a number of special rules for amending non-proliferation treaties. Michie concludes that the regime for the provisional application of non-proliferation treaties tends to be tailored to the subject matter of these treaties and the need for confidence-building among their parties. White finds that the methods of treaty interpretation applied in the area are essentially the same as in general international law. Myjer and Herbach highlight unique monitoring and verification mechanisms, given that a ‘breach’ of a non-proliferation treaty may be particularly difficult to ascertain. Joyner and Roscini observe a consistent practice of inserting special withdrawal clauses—particularly the ‘extraordinary events’ clause—in non-proliferation treaties.

Moving on to State responsibility, Happold argues that the general international law on State responsibility has little practical relevance in relation to disarmament obligations, as non-proliferation law is focused on prevention and compliance monitoring rather than reparation. Fleck focuses on a particular aspect of State responsibility—the legal consequences of withdrawal from a non-proliferation treaty—and identifies a series of unique mechanisms to address such a situation. Singh examines various ways in which non-proliferation treaties diverge, sometimes slightly and sometimes significantly, from the regime of countermeasures under general international law.

In reading Joyner and Roscini's book, the answer to the question whether or not non-proliferation law is sufficiently special to justify its qualification as a ‘special regime’ of international law becomes almost secondary. The contributing authors approach their respective chapters with measure and nuance, and the result is a most informative assessment of the characteristics of non-proliferation law as a subfield within an increasingly diverse international legal order. In the course of the discussion, it also becomes evident that the ‘special’ and the ‘general’ are relative categories. Notably, both the law of treaties and the law on state responsibility recognize the peculiarities of ‘integral obligations’ by setting forth a special sub-regime within general international law.

This nuanced approach makes the book a welcome contribution to the fragmentation debate, which has come to focus on the manners in which different regimes evolve and interact, both with one another and with general international law. What the book does not do is to reach beyond an analysis of ‘black-letter’ legal rules that constitute the non-proliferation regime. The book does little to contextualize the various peculiarities of non-proliferation treaties by relating them to the political events that have led to their creation and perpetuation. However, an edited volume can only accomplish so much, and this limitation in focus should not distract from the many strengths of the book. Non-Proliferation Law as a Special Regime is a very worthwhile read for both those with an interest in fragmentation theory and specialists in non-proliferation law.