In his ‘Preface and Acknowledgements’ the author explains that this book is based on a doctoral thesis presented in 2003 at the University of Sydney and is now revised and updated. He also explains his own involvement in the topic as ‘the result of personal and family experience’, which leads him to look at the question of multiple nationality primarily from the standpoint of the individual. His experience of international humanitarian law as an official at the International Committee of the Red Cross confirms this. On this basis, Boll deals with multiple nationality in a novel and interesting way: by an examination of state practice and nationality legislation, he reaches conclusions as to how States' acceptance of multiple nationality affects or creates rules of international law. As he states himself, ‘[T]he present study attempts to break new ground in several respects …’ (51). By analyzing the consequences of nationality on the municipal plane he ‘seeks to delineate the effects of state practice in light of opinio juris in terms of the rules of international law related to nationality …’ (3). In the author's reference to opinio juris the international lawyer will understand that he is referring to state practice as evidence of international customary law. Or perhaps he is applying an alternative monistic theory of international law, which ‘asserts the supremacy not of international law, but of municipal law’, as described, and dismissed, in Robert Jennings and Arthur Watts (eds) Oppenheim's International Law (9th edn, Oxford University Press, 2008) at 54, note 2. Boll frequently refers to his methodology, but the balance he strikes between national and international law, and between individuals and governments, is a fine one indeed.

Before turning to the contents of the book, some remarks on the wording of the title. Firstly, the use of the term ‘multiple nationality’. The author follows, quite correctly, what has become common usage among international lawyers. It is a curiosity, however, that the word ‘multiple’ is not in this connection understood as ‘many’ as in the everyday use of many meaning more than two, but as the author explains, at 2, the ‘book addresses not just “dual nationality” but any “multiple nationality.”’ This usage dates at least from the League of Nations Nationality Convention, 1930, article 5, which refers to ‘a person having more than one nationality’. However, the term plural nationality may, and is, frequently used in place of multiple nationality, and also the author quotes the use of ‘dual or multiple nationality’, as in the International Law Commission (at 208, note 124). Nevertheless, he himself consistently refers to ‘multiple nationality’ even where the source cited is dealing with dual nationality, as in the opening quotation. This is to point out that the reader should not expect any special treatment of the legal status of persons possessed of more than two nationalities.

Secondly, it may be noted that ‘international law’, as used in the title, refers to international public law and expressly excludes private international law, ‘also known as conflicts of law’ (3). In this way it does not fill the gap left in the European Convention on Nationality, 1997, as explained in paragraph 13 of its Explanatory Report: ‘The most important area which it has not been possible to include in the Convention relates to conflicts of laws arising from nationality.’ This explains, too, why the author has made scant use of the jurisprudence of the Iran-United States Claims Tribunal. For example, his treatment of Case A/18 omits the Tribunal's analysis of article 4 of the 1930 League Convention, the ‘non-responsibility’ article, and the caveat contained in it.

Thirdly, the title does not indicate that nearly half of the volume is comprised of an ‘Appendix: Overview of state practice’, covering an analysis of the nationality legislation of 75 states. Thus, the text runs from pages 1 to 308 and the Appendix from pages 309 to 566. The Appendix admirably supplements the wealth of individual case studies, taken mostly from the daily and weekly press and presented in the text.

In Chapter 1, on The Context and Significance of Multiple Nationality, Boll presents his basic assumption that multiple nationality exists and is even inevitable. However, as the possession of more than one passport is a sign of what used to be called in a negative sense an individual's ‘divided loyalties’ then, as pointed out, multiple nationality involves emotional issues. However, questions of loyalty and allegiance are now increasingly being discussed in the framework of human rights (8). At the same time, the author states that international law in respect of nationality is in many ways uncertain (13), so, as his aim is to discern rules of international law on an analysis of national legislation he here explains his choice of the countries, and questions put in the template, presented in the Appendix.

Chapter 2 reviews Views of Nationality, Citizenship, Ethnicity and Identity. The author points out the difference between nationality and citizenship, the former more generally a term of public international law, the latter of municipal law. Yet some overlap remains (as at 149). In general, he casts his net wide, going back to Greek and Roman ideas of citizenship as well as considering the historico-biological approach, which takes into account the historical, cultural and social ideal of the nation, the importance of ethnicity and sense of identity.

In Chapter 3, Nationality in Municipal and International Law, the author summarizes the significance and consequences of nationality in municipal and international law, while at the same time acknowledging that the following summary is not an exhaustive précis of nationality in international law. On the whole, he makes it clear that there are no limits on the discretion of states, such as stating that ‘states have basically unfettered freedom in determining whom they consider as nationals’ (98). Further, states are free to extradite, or not to extradite, their nationals, and are free to espouse, or not to espouse, their nationals' claims in cases of diplomatic protection. He gives interesting examples, but occasionally his statements are misleading, as when he writes, ‘The principle of equality as presented in the 1930 Convention is hard and fast’ (119). He is referring to the ‘non-responsibility’ article 4, mentioned above.

Chapter 4 is entitled Views and Treatment of Multiple Nationality in Historical Perspective and the Influence of Human Rights, and is the longest chapter in the book. As throughout, the author presents and deals with a wide and extensive variety of material, starting from the writings of Vattel.

Chapter 5, Principles of International Law that Govern Nationality and Areas of International Law Influenced by Multiple Nationality, and Chapter 6, Conclusion: the Relevance and Role of Nationality in International Law, both sum up and outline conclusions drawn from his text and from the survey contained in the Appendix. Human rights lawyers in particular will be saddened to read the author's conclusion that ‘current state practice toward multiple nationality is arguably to strengthen and confirm the reserved domain in terms of states’ discretion in matters of attribution and withdrawal of nationality in their municipal legislation' (278). He finds, too, there is ‘lack of a clear and universally accepted standard in relation to the opposability of nationality in cases of multiple nationality’; a strange conclusion considering he has not consulted the relevant international jurisprudence where such cases of opposability arise, as for example in the Iran-United States Claims Tribunal. In addition, at 280 he writes that, ‘probably unfortunately,’ there is no rule of international law prohibiting states ‘selling’ their nationality and at 281 that it ‘has always been relatively easy for states to denationalise individuals.’ For current practice he cites Saddam Hussein's ‘nationality correction policy’, as applied to 350,000 Shia Muslim refugees in Iran in 2001. On the other hand, following Paul Weis's Nationality and Statelessness in International Law (2nd edn, Stevens and Sons, 1979) he argues that states cannot impose their nationality on non-nationals without some expression of individual will or consent on their part (280).

Some special points invite comment or correction. For example, at 196 the author refers to ‘the Harvard Law School project that prepared the draft convention for the 1930 Codification Conference’ of the League of Nations. To call it the draft convention is incorrect because the Harvard draft Convention on Nationality, 1929, was, as the Director, Manley O Hudson, pointed out in his General Introduction, ‘wholly unofficial’, in spite of the overlap with the codification work of the League.

Perhaps, too, one may question the characterization of nationality jure sanguinis as based on ‘ethnicity’ and hence discriminatory and a violation of human rights. The attribution of nationality on the principle of jus sanguinis is universally accepted as one of the two modes of acquiring nationality at birth, together with that of the jus solis, and is part of general international law. It can in no way be compared with the Nazi racial laws. There are no racial requirements placed on father, or mother. This misleading argument is sometimes put forward—and Boll refers to it at 212—with reference to the revived, pre-Soviet, nationality laws of the Baltic States, and the united Germany, as they regained their sovereignty. The issue has been particularly confused in the case of the Baltic States—Estonia, Latvia and Lithuania—for two reasons. Firstly, in the Soviet Union dual nationality was not tolerated, and citizenship was accorded as between the fifteen constituent States on the basis of domicile, or residence. There is no right in international law, on the other hand, for those resident on the territory of a successor State to its nationality. Secondly, as the three Baltic States applied for membership of the Council of Europe in 1991, on regaining their sovereignty, the Council could, for purposes of ratification of the European Convention on Human Rights, a sine qua non for membership, scrutinize what they took to be the human rights record of the three States. Such regional rules, based on a treaty régime, do not ipso facto create rules of general international law.

So, whereas the author's treatment of the topic from the viewpoint of international law is, frankly, disappointing, although this is in large part due to the limitations he sets for himself, and clearly states, he must nevertheless be thanked for the work he has put into this book. For one is left with the knowledge, so well demonstrated, that there are indeed problems connected with the status of multiple nationality: for individuals, for the community and for governments. Paul Lagarde, noted expert on French nationality law, has an article entitled ‘Droit de la nationalité et droit de l'immigration’, published in the Mélanges en l'Honneur de Nicolas Valticos (1999). In this, he concludes with the plea that immigration law and nationality law not be confused: the first is a question of policy or politics, and subject to change, whereas the latter involves the community as a whole, and should remain stable. Perhaps this is one proposal with which Dr Boll, now employed by the State Department in Washington DC, would agree.