It would be almost impossible to overstate the importance and influence of Christoph Schreuer in international investment law. The editors of the book under review refer to this importance by a witty observation that ‘While some have called his Commentary [of the ICSID Convention] the “Bible of Investment Law”, Christoph Schreuer would not be inclined to such designation, the most obvious – but not only – reason being that not everybody believes in the Bible (p. v)’. In terms of history of ideas, this might be read as an allusion to Vaughan Lowe's argument that the development of international law can to a certain extent be analogized to the development and subsequent secularization of religion.Footnote ¹ Schreuer's oeuvre might then constitute a fusion between a chronicle and a prophetic pronouncement, both authoritatively reflecting and possibly creating normative propositions in the field of investment law.Footnote ² Be that as it may, and leaving aside the tantalizing hint at the necessity for a (re-)examination of investment law from the perspective of religion,Footnote ³ Schreuer's Liber Amicorum explicitly posits itself as a statement of investment law for the twenty-first century. This review will take the title at face value, accepting the contributions as reflecting the contemporary mores of investment law and trying to tease out certain legal implications.

Two perspectives in particular will be considered here. First, the book under review will be considered in dynamic terms, employing it as a tool for situating contemporary international investment law on the temporal spectrum of development of international law. The fact that a Liber Amicorum of a general international lawyer can be exclusively devoted to international investment law necessarily presupposes at least two things: first, a certain maturity of the field of inquiry within which the juridical friendships have had time to blossom and, second, its relative importance if compared to other fields that would justify the exclusiveness. If one were to try to predict the broad contours of a Liber Amicorum in light of dedicatee's interests from the perspective of, say, the mid-1990s, while investment law would not be entirely absent,Footnote ⁴ the involvement of domestic courts with international law,Footnote ⁵ state immunity,Footnote ⁶ and theoretical questions about the nature of the international legal order might have been expected to receive greater interest.Footnote ⁷ Yet, the book under review is exclusively devoted to investment law (which Schreuer's writings effectively monopolized, Dolzer, p. 818), and his earlier research on domestic courts and state immunity is at most used as a starting point for discussing the operation of investment law in particular areas (respectively Liebscher, p. 105; Bjorklund, p. 302). If Libri Amicorum are taken as a benchmark in documenting the (relative) rise of investment law, the book under review is reflective of a broader trend. Ignaz Seidl-Hohenveldern also wrote extensively about investment lawFootnote ⁸ but his 1998 Liber Amicorum deals with a great variety of international-law issues.Footnote ⁹ Conversely, the recent dedications to Thomas WäldeFootnote ¹⁰ and Bernardo Cremades place considerable emphasis on investment law and arbitration.Footnote ¹¹ Investment law has come of age in more senses than one, and the book under review is both evidence of it and an erudite elaboration of the intellectual contours of this development.

The book under review is entitled Investment Law for the 21st Century. Judging the book from its cover, one might plausibly expect the contributions to address the developments of the last decade (although one might equally consider the title to be without prejudice to the temporal focus: investment law for the twenty-first century is not necessarily limited to the investment law of the twenty-first century). Most chapters indeed seem to follow the former reading, elaborating particularly in Parts II (Jurisdiction), III (Procedure), V (Substantive Investment Law), and VI (Regional Aspects of Investment Protection) the contributions of recent practice and arbitral decisions to the development of investment law. At the same time, James Crawford's chapter on ‘Continuity and Discontinuity in International Dispute Settlement’ makes a somewhat different argument, namely that ‘[t]he “brave new world” of international dispute settlement turns out to have a great deal of the old world in it too’ (p. 802). The first part of the review will take this proposition as a point of departure, somewhat hyperbolizing it for rhetorical value and suggesting that there is very little in the investment law for the twenty-first century that would extend in conceptual terms beyond the investment law of the nineteenth and last centuries.

Second, the book will be approached in static terms to consider the present state of investment law (scholarship) and what it says about investment law in particular and international law in general. The book may be read as a reflection of the confidence and maturity of the investment legal order. Most contributors tease out and elaborate fine and subtle juridical points within the existing rules and procedures, being implicitly satisfied with or at least certain about the sustainability of the broader structures of the status quo. Surely, as August Reinisch states in the first sentence of his concluding chapter of the volume (albeit qualifying it later), ‘Investment arbitration is a success story’ (p. 894). However, the successful twist to the story is at least partly predetermined by the almost exclusive focus on the arbitral interpretation of investment protection treaties. Arguments for alternative methodological approaches, greater reliance on non-investment international law, and reconstruction (or deconstruction) of investment law either in conceptual terms or through greater involvement of states and international organizations do not receive substantial attention by the authors. One might therefore need to further qualify Reinisch's starting point: investment law is indeed a success story but less uniformly so than a focus on its most successful bits might suggest.

1. Investment law before the twenty-first century

James Crawford concludes his chapter on continuities and discontinuities with the following two propositions:

Most chapters elaborate questions raised and answered by recent arbitral jurisprudence, so it seems only natural that, for them, the earliest temporal points of departure might be found either in the 1960s, in the materials relating to the conclusion of the ICSID Convention, or in the 1990s, when the first landmark treaty arbitrations took place. V. V. Veeder's erudite chapter on the linkages between German–Soviet treaties of 1918–25 and the settlement of disputes relating to German concessions shifts the focus to pre-Second World War practices. Still, despite the confident sound of its title (‘The German-Speaking Origins of the 1965 ICSID Convention’), the chapter concludes on a cautious note: continuity between the 1920s on the one hand and ICSID and New York Conventions on the other hand appears to exist less on the level of rules and institutions and more in terms of ‘the same fertile soil’ of ‘a common legal culture’ underpinning these developments (pp. 398–9). While an important argument in favour of continuity between pre- and post-Second World War investment law, Veeder's evaluation of the contribution is much more qualified than in his famous article about the Lena Goldfields arbitration that was contemporary with those events.Footnote ¹²

James Crawford's chapter about continuities in international disputes also raises a broader question about the themes addressed in the book: how ‘deep in the historical experience of international law’ should one search for the roots of investment law? One, rather extreme, way of answering the question might be to go as far back as 1360 – a not entirely arbitrary starting point for thinking about the development of investment law, in light of the composition in this year of Giovani de Legnano's Tractatus de Bello, de Represaliis et de Duello. Footnote ¹³ Despite having been written at a time in which only the most embryonic elements of the future international legal order could be detected as emerging,Footnote ¹⁴ breaches discussed (denial of justice) and procedural solutions proposed (direct right of the injured individual to apply reprisals after an ex ante confirmation by the prince and with an ex post review by a judge) bear some resemblance to the challenges of contemporary investment law, qualified for the objective differences in the available institutions through which comparable policies could be implemented.Footnote ¹⁵ Even then, the focus on the property to be taken in the process of reprisals reflected the practical concern of protecting merchants trading in other polities.Footnote ¹⁶ Stephen Schwebel notes denial of justice as still a ‘well-established’ ‘violation of international law’ (pp. 519–520), and de Legnano's policy concern about absence of control over an individual's procedural conduct was reflected in the important OECD Draft Convention on the Protection of Foreign Property that provided for the home state's right to preclude the investor's claim.Footnote ¹⁷ This is not the place to compare the pre-international-law and twenty-first-century international-law regimes in detail; it is sufficient to note that, if one were to accept the counterintuitive proposition that the roots of contemporary investment law might be found in these very archaic practices for the protection of commercial interests abroad, certain underlying premises in the historical narrative of investment law might need to be re-evaluated.Footnote ¹⁸

If the answer about the roots of investment law were to be sought within the four corners of traditional international law, it would not be a great exaggeration to say that not much of interest took place in the field from the time of de Legnano to the mid-nineteenth century. While the great and the good of international law did refer to denial of justice in the context of reprisals (which the rise of the state eventually transformed into exclusively public ones), they generally fell back on the chronicled style of classical Greek and Roman and religious history, with the normative propositions expressed in brief and abstract definitional terms of an ipse dixit character.Footnote ¹⁹ It is only the international law from the mid-nineteenth century to the Second World War that finally provides a relatively straightforward case of elaboration of investment law where content of rules of international law is determined by reference to traditional sources and methods. The first phase of facilitation of customary law-making is provided by the systematization of state practice and arbitral decisions on issues relating to the treatment of aliens, particularly in the great US digests.Footnote ²⁰ Interestingly, the availability of extensive materials did not significantly influence the still generally concise and definitional style of pronouncements in the leading legal writings, borrowing the formulations from earlier writers rather than going directly to state practice and cases.Footnote ²¹

Further elaboration of law took place in two very different ways that might be instructive also for the twenty-first century. On the one hand, in light of apparent agreement about the basic premises, focus shifted to finely detailed aspects of law. The increased sophistication of inter-state arbitrations (the 1903–05 Venezuelan CommissionsFootnote ²² and the US–Mexico General Claims Commission were particularly influential)Footnote ²³ led to an identification and explanation of increasingly finer points of law. These developments were also reflected in the legal writings, moving from mere descriptive systematization of practice that could not lead to precise definitions of the rulesFootnote ²⁴ to analysis of procedural and substantive issuesFootnote ²⁵ and, particularly in the 1930s, detailed consideration of particular obligations.Footnote ²⁶ Rigorous methodology that goes to finer substantive and procedural points within a regime that has an increased focus on arbitral and judicial decisions is not entirely unlike the approach taken by most contributions in the book under review.

However, and simultaneously, sophistication of analysis in elaboration of finer points did not go hand in hand with a consensus about the underlying processes of elaboration and application of the rules. In 1930, the Hague Conference for the Codification of International Law attempted to codify the law on state responsibility, understood at that point as also including the primary rules on the treatment of aliens. The debates during the conference turned away from the scope and content of the obligations of treatment to preliminary and basic questions about the nature of law-making processes through which custom and general principles could be created and identified.Footnote ²⁷ The issues raised seemed inexplicable to the established international lawyers presentFootnote ²⁸ but these discussions ultimately took up five of the available 12 days. The suspicion of traditional respondent states about the abusive character of earlier law-making practices was one of the reasons that contributed to the failure of the project.Footnote ²⁹ The Hague Conference shows how elaboration of fine points by sophisticated tribunals and legal writers can take place simultaneously with rejection or at least serious criticism of underlying premises by (a significant part of) the lawmakers: the Hague Conference is a contemporary and sometimes a successor of the awards of the US–Mexico Commission that are often cited in investor–state arbitrations as authoritatively stating the classic law.

The Second World War might serve as a dividing line between the traditional and modern investment law, with the modern rules reflecting both continuities and discontinuities with the classic regime (Crawford, pp. 801–17). With only slight exaggeration, it is suggested that, at the level of legal rules and institutions, continuity is so strong that it is complicated to identify much that would be original about twenty-first-century investment-protection law. As James Crawford demonstrates, fragmentation of rules and proliferation of tribunals were well-known phenomena to traditional international lawyers (pp. 801, at 816–17). One is tempted to pursue this line of thought further, in relation to other aspects of investment law that are sometimes considered to be innovatory.

There is little new about investment-protection obligations: rules on national treatment, most-favoured-nation treatment,Footnote ³⁰ and fair and equitable treatment may be traced to seventeenth-century treaties;Footnote ³¹ the most famous cases on expropriation date precisely from the first third of the last century. In terms of proliferation of and conflicts between adjudicators, it is questionable whether any investment adjudicator has faced challenges similar to 1903–05 Venezuelan arbitrations: arbitrating pari materia disputes against the same respondent in 11 parallel commissions,Footnote ³² expressly disagreeing about perhaps the most controversial legal issue of the time – attribution to the state of the conduct of insurrectionists – and using different imaginative arguments to harmonize the case law.Footnote ³³ The concept of prospective agreement of dispute settlement was recognized most prominently in the Statute of the Permanent Court of International Justice. Individual access to international adjudicators was also accepted in treaty-making,Footnote ³⁴ sometimes producing extensive case law.Footnote ³⁵ Even the project of ‘depoliticization’ of international disputes by providing individual access to international courts or tribunals, despite some uncertainty about its precise contours in contemporary practice,Footnote ³⁶ was well appreciated by the participants of the classic international legal order.Footnote ³⁷ In his chapter on the 1920s disputes about German concessions, Veeder also notes that ‘[i]n the USSR, as in Germany, there remained no mutually acceptable alternative to transnational arbitration for international trade disputes’ (p. 397). From this perspective, modern investment law is innovative only, if at all, in the way in which it combines otherwise run-of-the-mill rules and institutions.

At the same time, from the perspective of historical development of international law, modern investment law does pose certain peculiar challenges. The previous sections sketched the historical wavering of law on the protection of foreign commercial interests between the pragmatic legalism of de Legnano and the concise definitions of the later writers, from Gentili and Grotius up to Oppenheim. In the century or so between the mid-nineteenth century and the Second World War, the digests of (US) state practice provided investment law with the material sources, the increasing number of awards, and some writings engaged in preliminary systematization, and particularly the first third of the last century already proceeded to elaborate and analyse subtler issues through adjudication and legal writings. This background leaves the post-war and particularly twenty-first-century investment law in somewhat of a bind. It does not have (obvious) materials of practice of its own, and it no longer looks to John Basset Moore for guidance: unlike Grotius, who could comfortably draw on analogies from Greeks and Romans,Footnote ³⁸ for the twenty-first-century investment law, even early last century already seems a foreign and distinctly unrecognizable country.Footnote ³⁹ Some (early) awards of investment treaty tribunals responded to this challenge by adopting the conciseness of the classic writers and nineteenth-century practice and awards. Finally, similarly to the early last century, legal writings and later arbitral awards elaborated the applicable rules in nuanced and sophisticated terms. The work of Christoph Schreuer, particularly the commentary of the ICSID Convention, fits precisely within this stratum of thought.

There is also a feeling of a normative déjà vu to the 1930s with its simultaneous sophistication and uncertainty about the premises.Footnote ⁴⁰ The situation might be even more challenging this time: in the 1930s, the criticisms related to the authority of existing practice and case law and the meta-rules for transcending their narrative, while, in contemporary law, it is not necessarily clear where identifiable and relevant state practice could come from.Footnote ⁴¹ When lawmakers do attempt to tinker with or within the instruments that have been or might be put in place, the response of the investment lawyers seems mixed. Within the book under review, Schwebel describes the recent US practice as ‘an exercise in the regressive development of international law’ (p. 519), while L. Yves Fortier praises the Canadian ‘negotiation of innovative procedural protections and a robust dispute settlement framework – of which ICSID arbitration now comprises an integral part’ (p. 543). Given that the United States and Canada are perceived as having suffered the same shock of the traditional home state appearing as respondent in North American Free Trade Agreement cases, this is clearly a field in which reasonable people and states can disagree about lessons to be drawn. The focus of analyses of most contributions is certainly on the operation of the investment-law regime rather than the underlying questions of sources and law-making. This might simply suggest the maturity and robustness of the regime and the relative unimportance of meta-questions; still, the 1930s provide a good reminder that sophistication by experts within a regime might be easily combined with dismissal of the regime as such by lawmakers.

When discussing the development of international law from the perspective of history of religion, one of the later stages in Vaughan Lowe's taxonomy was the review of runaway prophecies. In international law, this process is exemplified by the list of sources in the ICJ Statute and the codificatory work of the ILC.Footnote ⁴² Within the four corners of this argument, the logical next step of investment law should entail a review of practice and case law, identifying the correct meta-rules and, pursuant to those, the worthy arbitral pronouncements. With this perspective in mind, the emerging order might already be glimpsed in the treatise of Zachary Douglas on investment claims, formulated in terms of systematized principles,Footnote ⁴³ and the work of the International Law Association's Study Group on the Role of Soft Law Instruments in International Investment Law. Within the history of general international law, the codes by private authorsFootnote ⁴⁴ and professional bodies of the late nineteenth centuryFootnote ⁴⁵ paved the way for the 1899 and 1907 Hague Conferences. It remains to be seen whether and how states (and increasingly also international organizations) will engage in the review and revision of existing investment law.

2. Investment law of the twenty-first century

In the oral proceedings relating to the Reparation for Injuries Suffered in the Service of the United Nations, Gerald Fitzmaurice described his preferred method of approach as a negative one: ‘In order to ascertain what a thing is, it is sometimes very useful to begin by enquiring what it is not.’Footnote ⁴⁶ This might also serve as a useful perspective for discussing the vision of investment law of the twenty-first century reflected in the book under review, focusing in particular on the arguments that do not receive as much attention as one might have expected. There seem to be at least four types of issues that might not be perceived as belonging to ‘proper’ investment law: law of treaties and international responsibility, customary law, human rights law, and arguments falling outside the four concerns of legal reasoning. These points will be considered in turn.

First, despite having a whole Part VII entitled ‘Investment Law and Other Fields’, the definition of ‘otherness’ and the appreciation of its possible contribution seem fairly narrow. One class of issues addressed under the rubric of ‘otherness’ relates to the relevance of the law of treaties (on provisional application and interpretation) and of the law of state responsibility (on circumstances precluding wrongfulness and joint responsibility) to the application of investment law (Hafner, pp. 593–607; Binder, pp. 608–30; Qureshi, pp. 631–5; Wittich, pp. 708–23; Wälde, pp. 724–81). While one should probably not read too much into the taxonomy of contributions into different parts, classifying law of treaties and law of state responsibility that bear on the application of investment law as ‘other’ could suggest a very narrow, perhaps even isolationist, vision of what ‘proper’ investment law is. The sophisticated analyses of chapters themselves demonstrate how indispensable the law of treaties and law of state responsibility are in identifying the existence and scope of obligations and consequence of their breaches. In the years after the publication of the book under review, arbitral jurisprudence has further demonstrated how whole cases might turn on such fine meta-issues: how to classify non-precluded-measure treaty clauses in terms of taxonomy of primary and secondary rules,Footnote ⁴⁷ whether a treaty interpreter can rely on customary law only if custom addresses precisely the same issue,Footnote ⁴⁸ what the secondary rules of preclusion of wrongfulness really mean,Footnote ⁴⁹ and how provisional application of treaties operates in investment treaty arbitration.Footnote ⁵⁰ It is perfectly clear that investment law cannot (any longer?) afford to treat law of treaties and responsibility as something ‘other’ than investment law, and not only in the sense of investment law being part and parcel of traditional rules and methods of creation and application of international law: in very utilitarian terms, such arguments are quite likely to be determinative in how actual cases are argued and decided.

Second, another aspect of investment law that does not receive much attention is customary international law. In light of Parts I–VI, one is tempted to situate the heart of ‘proper’ investment law in investor–state arbitration decisions, particularly those interpreting treaty obligations. The customary law of diplomatic protection is addressed in two contributions by Peter Muchlinski and Abby Cohen Smutny (respectively at pp. 341–62 and 363–76) but both authors are explicitly sceptical about the relevance of the regime: for Muchlinski, ‘[d]iplomatic protection amounts to a rather limited and anachronistic method for the resolution of investment disputes’ (p. 362) and, for Smutny, it is the lex specialis of the investment treaty that is the controlling legal standard for investment claims of shareholders (p. 376). The role of customary law in the determination of substantive obligations is addressed in Schwebel's contribution on denial of justice (pp. 519–21) but in a rather cursory manner, without elaborating the development of the contours of this primary rule by arbitral tribunals. The simplest explanation for the relative disregard of customary law might be that the topics in which customary law might play a greater role – fair and equitable treatment and expropriation immediately come to mind – have not been addressed by the authors.

At the same time, the preference itself might be seen as reflecting an unarticulated assumption about the sufficiency of the four corners of the particular treaty text(s) in answering legal questions raised in investment arbitrations. As was suggested above, law of treaties and international responsibility might have considerable practical importance and, in most cases, these rules would exist in the form of customary law. More broadly, while the explicit language of treaty rules might be sufficient to resolve normative queries in many circumstances, an exercise in treaty-making is always made within the broader fabric of law of treaties and automatically comes with Article 31(3)(c) of the Vienna Convention on the Law of Treaties that points to ‘other relevant rules’. The differences in the subject matter and content of customary law and treaty rules do not necessarily exclude custom from the interpretative exercise. Regarding the similarity of the subject matter, Bruno Simma and Theodore Kill note that ‘[a]lmost any rule of international law will be “relevant” when considered with the proper degree of abstraction’ (p. 696). The differences in content between treaty and custom might be said to properly relate to the role that custom might play in the interpretative exercise rather than to the ab initio question of its admissibility as an interpretative material. Even customary rules that do not conclusively resolve the particular issue might at the proper degree of abstraction perform a useful contextualizing role in the interpretative process.Footnote ⁵¹ Consequently, when duly qualified for the differences in function and content of treaty rules, customary law (on, say, expropriation, denial of justice, full protection and security, other aspects of the international minimum standard, and the rules of admissibility) might be usefully employed in the interpretative process, without prejudice as to whether the result of the process will be to confirm the distinctiveness of treaties or to illuminate the ambiguities in their rules.

The third type of argument that is not prominently present in the book concerns to the relationship of investment law with other regimes of international law (like environmental law and trade law). The exception is human rights law, which is addressed in three erudite contributions. Two of them deal with the practice of the ECtHR in matters of property protection and investment (Tomuschat, pp. 636–56; Wildhaber and Wildhaber, pp. 657–77), while Judge Bruno Simma and Theodore Kill propose ‘First Steps’ in formulating an interpretative framework for dealing with human rights from the investment-law perspective (pp. 678–707). In particular, Judge Simma and Kill suggest that human rights law might be used in the interpretative process both in establishing the meaning of specific rules of investment law and in presuming compliance with human rights law (pp. 703–7). The first aspect of this proposition might be particularly fruitful when investment protection and human rights obligations run in parallel.

The application of this model might significantly extend the scope of admissible interpretative materials. For example, in the Saluka case, the Czech Republic simultaneously owed two obligations regarding deprivation of investments: an obligation under Article 5 of the Dutch–Czech BIT to the Netherlands (and perhaps also to the investor), but also an erga omnes partes obligation under Article 1 of Protocol 1 of the ECHR to the investor and to all parties to the Protocol.Footnote ⁵² In the Mondev and Loewen cases, the United States owed an obligation regarding the administration of justice both under Article 1105 of NAFTA and under customary law to Canada (and perhaps also to the investors), but also an erga omnes partes obligation under Article 14 of the ICCPR to the investors and to all parties to the Covenant.Footnote ⁵³ It is complicated to see why, even under the strictest possible construction of Article 31(3)(c), these parallel human rights obligations would not be ‘relevant’ in such circumstances, with potentially significant effect in the interpretative process.

Such a solution would be in line with the view dominant in the immediate post-Second World War years that human rights should be used to ‘concretize’Footnote ⁵⁴ and ‘clarify’ the international minimum standardFootnote ⁵⁵ (before García-Amador doomed the argument by his proposal in the ILC to simply merge both bodies of law).Footnote ⁵⁶ The methodology has also been accepted by the Tribunal in the Toto Construzioni Generali S.P.A. v. Lebanon case, interpreting the investment obligations on denial of justice by reference to the ICCPR.Footnote ⁵⁷ This is not merely a question of whether certain analogies are useful: if the human rights rules are ‘relevant’, Article 31(3) of the Vienna Convention states in imperative terms that they ‘shall be taken into account’. It is certainly important to presume compliance of investment treaties with other international obligations, as explained by Judge Simma. However, it is at least as important to employ the interpretative potential of structurally and substantively comparable human rights obligations that point in the same direction as investment law and require the host states to treat investors and investments in a certain manner.

Fourth, most contributors clearly situate themselves within the four corners of legal reasoning and traditional sources of international law. There is nothing on international law and empirical studies. There is not much written on international law and international relations, or on novel concepts like global administrative law or global constitutional law. The closest that one gets to arguments that would have raised Lassa Oppenheim's eyebrows is in Moshe Hirsch's subtle analysis of an IR perspective of compliance with investment treaties (pp. 865–93; Keyvan Rastegar's and Ernst-Ulrich Petersmann's chapters might be read as either innovative rethinking of the mainstream view of interpretation or an argument for something radically different, respectively, pp. 278–301 and 877–93). This is a book by international lawyers for international lawyers.

It is a pleasure to read a collection of contributions of such high quality that leaves aside the otherwise interesting policy perspectivesFootnote ⁵⁸ and engages in solid analysis of lex lata. The only regret is that most contributions address issues that, while of considerable importance in the particular area, might not necessarily raise questions of broader interest, like the contributions of Andrés Rigo Sureda on precedents and Reinisch on possible improvements of the investment-law system do (respectively, pp. 830–42 and 894–916). It is interesting to speculate what the contributors might have said, had they turned their inquisitive pens and analytical minds to some more controversial questions that cannot necessarily be answered by choosing the most persuasive of a number of awards like, say, relationship of fair and equitable treatment and customary law or the development of customary law on the minimum standard and expropriation.

Nevertheless, while one might query the perhaps excessive focus of the book under review on arbitral interpretation of treaty rules, the investment case law is the most visible and fastest-developing part of a remarkable regime. The only qualification that one is tempted to make is that it is neither the only one nor necessarily the most important one in the long term. Investment law consists of harmonious and conflicting multitudes of other authorities, including customary-law obligations; meta-rules of treaty law and secondary rules of state responsibility; substantive and procedural rules on human rights, trade, and the environment; and, above all, the law-making and procedural capacities of states and international organizations. The most significant challenges to the insularity of investment law might come from the direction of European Union law (Wierzbowski and Gubrynowicz, pp. 544–60) – a regime that so far has not demonstrated a tendency to engage in subtle and respectful co-operation with other international adjudicators.Footnote ⁵⁹

The story of investment law, as sketched out in the previous sections, consists of concentric circles of tension: tension between the pragmatic legalism of de Legnano and the dogmatic approach of his successors; tension between the law reflected in the state practice and case law of the nineteenth and early in the last century and the rejection of its underlying premises; and the recent tension between the decentralized adjudicators on the one hand and lawmakers and broader systemic considerations. The problems plaguing investment law are not new, and they are not even old – they have always accompanied the law on protection of commercial interests beyond the boundaries of the particular polity. Perhaps that is the best explanation for why secularization (if one is permitted to use the witty remark about the biblical authority of Schreuer's writings to return to the perspective of history of religion)Footnote ⁶⁰ might only lie in the future of investment law, and the present regime will still be inhabited by a jolly collection of legal fundamentalists, heretics, pagans and atheists (without prejudice to how the existing schools of thought should be taxonomized under these headings).