The international law of jurisdiction is by and large customary law, fragmented and often indeterminate. This ambitious book, based on Cedric Ryngaert's PhD at Leuven University, does not disappoint. Its aim is nothing less than a comprehensive analysis of the admissible geographical reach of State legislative power.

After deploring the ‘compartmentalization of the law of jurisdiction’,Footnote ⁸ the tendency for separate jurisdictional rules and analysis of them to develop in isolation from each other in different areas of international law, the study distils common principles of jurisdiction from diverse areas of law, including competition law, criminal law, securities law, export controls, discovery and human rights. The study's focus is on transatlantic jurisdictional wrangles, and limited to US and European State practice. The author weaves in decisions and writings from a range of countries and languages. This comparative approach is testament to his broad immersion in the material though there are occasional lapses, for instance the translation of the German ‘umstritten’ (controversial) as ‘most important’Footnote ⁹.

In the introduction, the author explains why jurisdiction is a central concern of international law. He notes the pejorative connotation of the term extraterritoriality, the regulation of matters not solely within the domestic sphere, and expresses strong reservations about that term: ‘The term “extraterritoriality” is confusing, however. “Extraterritorial jurisdiction” ought to imply that a State exercises its jurisdiction without any territorial link (‘extra-territorial’), albeit the expression is typically used in a context of States asserting jurisdiction on the basis of some, admittedly non-exclusive, territorial link.'Footnote ¹⁰ His preferred term is unilateral jurisdiction. Despite his scepticism about the term ‘extraterritorial’ however, the author uses it throughout the book.

In Chapter 2, an overview of how public international law approaches jurisdiction, the starting point is the Permanent Court's broad view of permissible jurisdiction in the Lotus case and the persistent influence of this view, despite sometimes contrary State practice and academic criticisms. Ryngaert then traces out the historical origins and modern tendencies of the territoriality principle in Chapter 3. Chapter 4 is devoted to extraterritorial criminal jurisdiction, with an in-depth treatment of the universality principle, a controversial head of jurisdiction that the author endorses wholeheartedly His enthusiasm for universal jurisdiction may explain his attempt to fit this concept within a territorial paradigm, leading to the confusing expression that universal jurisdiction may be premised on the ‘anticipatory legality from the anticipated territoriality of a later fully-fledged prosecution and possible trial’.Footnote ¹¹

Readers are likely to agree with the author's diagnosis that in our interconnected world, the extraterritorial exercise of jurisdiction, which the author also refers to as ‘unilateral’ is ‘nearly inevitable’.Footnote ¹² In Chapter 5, the author examines a number of principles that could restrain extraterritorial jurisdiction, including comity, genuine connection, equity, proportionality, abuse of rights and above all reasonableness. Reasonableness, as contained in the Restatement (Third) of US Relations Law, is not a rule of law. In Ryngaert's view, however, jurisdictional reasonableness is key to preventing jurisdictional overreach. In Chapter 6, Ryngaert spells out his own theory of jurisdiction: ‘a fairer and more efficient rule of reason’.Footnote ¹³ States should exercise jurisdiction reasonably in line with the interests of the international community, ‘as if they were a global regulator who objectively assesses the merits of any one State's legal and policy interests’Footnote ¹⁴ from the distinct viewpoint of global welfare. He advocates a general principle of international subsidiary jurisdiction, which would operate only if the State with primary jurisdiction—the one with the most reasonable connection—neglects its responsibility. Even though the author relies heavily on the notion of optimal global regulation, he does not specify a clear theory of regulation that could assist the reader to evaluate his plea for a global perspective. He does not substantiate why his proposal is fairer and more efficient. One potential concern is that the orientation towards a global interest could prevent courts from reaching efficient solutions tailored to local conditions especially when voter preferences differ.

Traditional international law on jurisdiction is said to be extremely malleable, leaving free reign to regulatory home bias. The book holds out a utopian benchmark where States exercise jurisdiction solely in the interest of furthering global welfare, based on specific jurisdictional rules for each field of law. In this brave new world, the unilateral exercise of jurisdiction assumes a multilateral character, and reduces the need for substantive harmonization, treaty-making or institutional international cooperation, each of which may be fraught with difficulties. Courts and parliaments shed their home bias, and focus instead on the global interest. Lawyers leave behind their ingrained belief in the superiority of their own law. The chief conduit for his silent legal revolution is transnational networks, as championed by Anne-Marie Slaughter in A New World Order. Ryngaert advances a powerful plea that a new international law of jurisdiction could become a reality through regular contact between judges, parliamentarians, regulators and civil servants and the resulting cooperation and accommodation of divergent interests. It may be open to doubt, however, whether such networks, composed largely of elites with varying interests and beholden to their own voters, will able to coalesce around an ill-defined ‘global interest’ in any given policy area.

Regrettably, the author occasionally lapses into stereotypes. The juxtaposition of US unilateralism and European multilateralism is too crude, for instance, when the author asserts that ‘European States shy away from projecting their extraterritorial regulatory power abroad in the first place’,Footnote ¹⁵ or when interest balancing under jurisdictional reasonableness in the US is presented as the polar opposite of the European, allegedly much more rules-based analysis based on connections to the forum State. Surely, the ‘European’ approach still leaves plenty of room for policy considerations, even though European judges might be more reluctant to bring these into the open. Even more striking is the assertion that the United States desires stricter regulation and Europe opposes stricter regulation.Footnote ¹⁶ To many readers on both sides of the Atlantic, this will seem an oversimplification against the grain of received wisdom.

In the introduction, the author explains that in public law matters courts do ‘not face the choice of applying forum law or foreign law’,Footnote ¹⁷ pursuant to the longstanding rule that courts do not apply foreign public law. Presumably, a major reason for this rule reflects a deep reluctance to apply the policies of another country. One is left wondering, even after having read the book, whether this is still a good rule in light of Chapter 6's plea for exercising jurisdiction based on the global interest. The author could have made an intelligent case for revisiting or even abandoning that rule. Ryngaert likely overstates the scope for conflict in case of concurrent jurisdiction. He seems to assume that concurrent jurisdiction invariably leads to international conflict, and that overlapping regulatory layers should be avoided at all costs. The reader is also likely to puzzled by the statement that ‘there is often not much of a dichotomy between private and public interests, since it is not unusual that the interests of governments on the one hand, and individuals and corporations on the other hands, coincide, especially in the field of economic law’.Footnote ¹⁸ Especially in economic law, the interests of the government and private actors quite often diverge.

Realists in particular may question the desirability and feasibility of a wholesale reorientation of the international law on jurisdiction based on the global interest. Those committed to multilateral institutions are unlikely to be convinced that his new theory of jurisdiction obviates the need for more institutionalized international cooperation. Even though one many disagree with Ryngaert on these and other details, this remarkably concise volume is a gem bound to become a reference on prescriptive jurisdiction in international law. It deserves a wide readership.