Jump to Content Jump to Main Navigation
Signed in as:

Part III Consent in Investment Arbitration, 15 Conclusion

From: Consent in International Arbitration

Andrea Marco Steingruber

From: Oxford Legal Research Library (http://olrl.ouplaw.com). (c) Oxford University Press, 2023. All Rights Reserved. Subscriber: null; date: 06 June 2023

Arbitral agreements

(p. 321) 15  Conclusion

15.01  Arbitration is considered to be a consensual dispute resolution mechanism. Party autonomy is fundamental for the existence of arbitration1 and is the primary source of the arbitration jurisdiction and the procedure. However, while the classical characterization of arbitration is still influenced by commercial arbitration,2 arbitration has evolved.3

15.02  With the growing acceptance of arbitration as a dispute resolution mechanism and its use in areas other than the traditional one of commercial arbitration, the consensual character of arbitration has been perceived as decreasing or, at least, becoming different.

15.03  The reaction to this evolution and changed perception of the consensual nature of arbitration differs: some authors would like to abandon the dogma of consent,4 others speak about the marginalization of consent,5 while others again suggest referring to a modern approach to consent.6 Moreover in the case of investment arbitration it has been argued that this type of arbitration is a consensual but not a contractual dispute resolution mechanism.7 Consent to arbitration is indeed a complex phenomenon.

A.  The Different Perspectives of Consent

15.04  Consent in international arbitration can be viewed under different perspectives. The reasons for analyzing consent in this way are:

  1. 1.  ‘consent’ is a multifaceted term: the definition perspective;

  2. 2.  arbitration and its consensual nature have evolved: the evolution perspective;

  3. 3.  arbitration is no longer a dispute resolution mechanism used only to resolve bilateral disputes between privates: the structural perspective;

  4. (p. 322) 4.  the ways of expression of consent to arbitration by each party, and of reaching mutual consent to arbitration may differ: the validity perspective;

  5. 5.  the scope of consent to arbitration may differ: the scope perspective;

  6. 6.  there is sometimes a tendency to enlarge the reach of consent to arbitration: the enlargement perspective;

  7. 7.  procedural needs may come into conflict with the consensual nature of arbitration: the procedural needs perspective.

1.  The definition perspective

15.05  ‘Consent’ is a multifaceted term. It may have the significance of the expression of consent or the reaching of mutual consent. Moreover the adjective ‘consensual’ is one of the essential criteria for arbitration’s qualification.8

15.06  While it is important to differentiate between the characterization of ‘consensual’ as one of the essential criteria for arbitration’s qualification and ‘consent’ as a condition for the validity of the arbitration agreement, these two aspects influence each other. Therefore, the interplay between the process of reaching mutual consent—first the unilateral expression of consent to arbitration by each party and then the reaching of mutual consent to arbitrate itself—and the consensual character of arbitration remains important. In fact, it is the process of reaching mutual consent which may influence the perception of the consensual character of arbitration.

15.07  In this book a proposal of classification of categories of consent has been made. This classification depends on two factors: on whether consent is directed to an individual person or to a group of persons and on whether consent to arbitration is expressed/reached after a dispute has arisen or before the breaking out of a dispute.9

2.  The evolution perspective

15.08  Arbitration has evolved. Over time there has been a move from an understanding of arbitration where consent was given by the parties after the dispute had broken out (compromis—submission agreement) to one where consent is expressed before the dispute has arisen (clause compromissoire—arbitration clause).10 This evolution brings a reduction in the pure consensual character of arbitration, but also a bigger acceptance of arbitration as a mechanism for the resolution of international disputes. Today, arbitration is considered the natural forum for the resolution of international disputes11 and in the field of investment arbitration the distinction between submission agreement and arbitration clause has lost its importance. Indeed in investment arbitration the host State expresses its consent before the dispute has broken out, whereas the foreign investor regularly expresses it after the dispute has arisen.

15.09  Over the years there has also been an expansion in parties’ freedom to arbitrate, ie of the domains considered to be arbitrable. Indeed, in recent years, the scope of rights amenable to arbitration has grown to such an extent that the concept of arbitrability has almost lost importance in today’s arbitration world.12

15.10  A further evolution has been the progressive abolishment of the restrictions on States’ entitlement to enter arbitration agreements (subjective arbitrability). States cannot rely on their own law to invalidate an arbitration agreement they entered into freely.13 The changing attitude and (p. 323) role of the State has modified the face of arbitration, as can best be seen with regard to investment arbitration. In investment arbitration States express their consent in national investment laws and investment treaties to resolve disputes with foreign investors through the means of arbitration (standing offers). In the case of investment treaties, the contracting States to the treaties also reach an agreement—international law-making—to use arbitration as a dispute resolution mechanism.14

3.  The structural perspective

15.11  The structural perspective is closely linked with the evolution of arbitration. The historical role of arbitration was that of an informal and bilateral dispute resolution process, particularly popular in linear bilateral commercial transactions, such as sale of goods and transport contracts.15 However, arbitrations involving complex jurisdictional issues have become commonplace.16 Often the traditional role and bilateral nature of arbitration cannot accommodate modern international transactions which take place in areas such as construction contracts, banking and financial transactions, reinsurance contracts, and transactions involving multinational corporations and States operating through State agencies or other emanations of the State. In complex situations consent to arbitration is frequently expressed by conduct.

15.12  In many areas arbitration is perceived to have a reduced consensual character. This is the case in the banking field, where unilateral arbitration clauses are important, or in charterparties and reinsurance contracts arbitration, where clauses incorporated by reference play an essential role. In the field of sports the perceived reduced consensual character is due to arbitration clauses contained in the articles of association of sports organizations.17

15.13  Nevertheless, when the process of reaching consent differs due to structural diversities or because mutual consent to arbitrate is reached through unilateral arbitration clauses, arbitration clauses by reference, or arbitration clauses contained in articles of association, arbitration is not a less consensual dispute resolution mechanism. Indeed on the one hand there are different ways of expressing consent to arbitration (by promise, by conduct) and on the other hand there are different types of contract. An arbitration agreement does not necessarily need to be a synalagmatic contract.

15.14  In investment arbitration the State regularly expresses its consent to arbitration in national investment laws or bilateral and multilateral investment treaties.18 In the last two decades there has been an exponential growth in the number of BITs and investment disputes.19

15.15  The particularity of investment treaty arbitration is that multiple parties are involved. Indeed the expression of the State’s consent to arbitration stems from an international treaty concluded by two—in the case of BITs—or more—in the case of MITs—contracting States. The host State makes, in advance, a unilateral standing offer (consent) to arbitrate. For States this has represented an evolution from retrospective to prospective consent to arbitration in the international context.20 The multiplicity of parties involved is shown by the fact that the host State’s offer has been considered by certain scholars, and also by some national courts, as a stipulation in favour of a third party (ie the foreign investors).21

(p. 324) 15.16  Moreover, the host State’s standing offer is made by a State to multiple potential private foreign investors. Indeed, several private foreign investors could be affected by the same measure taken by a host State. In investment arbitration there is a sort of ‘verticalization’ of arbitration, and a declining importance of the classic ‘mirror arbitration’ scheme. In fact, often it will only be the aggrieved investor that can bring a claim against the State. In other words, investment arbitration can be based on an arbitration agreement which takes the form of an unilateral contract and which is concluded once the foreign investor finalizes the expression of its consent by instituting the arbitration proceeding (expression of consent by performance).

4.  The validity perspective

15.17  Arbitration agreements are contracts. However, contracts may be of different types. They can be bilateral and synalagmatic, bilateral but non-synalagmatic, or unilateral. The same is true for arbitration agreements.

15.18  In commercial arbitration the parties express their consent by promise (offer and acceptance) or by conduct. Regularly the arbitration agreement is a bilateral synalagmatic contract, in which both parties have expressed their consent by promise. This is particularly so when the parties adopt model arbitration agreements of arbitration institutions. Nevertheless, it is also possible to have bilateral contracts in which parties express their consent by conduct.22 Such situations often arise in what are called multiparty situations. Yet not all arbitration agreements are bilateral synalygmatic contracts. Unilateral arbitration agreements are bilateral but non-synalagmatic contracts.23

15.19  In commercial arbitration mutual consent to arbitration has to be reached with regard to the essential elements, ie an agreement between the parties that any dispute between them will be resolved by arbitration, and an indication of the dispute or legal relationship, which will be the subject matter of arbitration.24 However other elements may also be of importance, for instance the seat of arbitration, the number and appointment of arbitrators, the language of the proceeding, and provisions for multiparty situations.25

15.20  While in traditional international commercial arbitration—administered by private institutions and even more so in ad hoc proceedings—the jurisdictional power of an arbitral tribunal stands entirely on the mutual consent reached by the parties on the essentials elements, in investment arbitration the situation is different. Indeed, in arbitration proceedings conducted under ICSID one cannot ignore the fact that ICSID jurisdiction is limited by the nature of the operation at hand, because objective jurisdictional requirements ratione personae, ratione materiae, and ratione temporis have to be fulfilled.

15.21  In investment arbitration the host State and the foreign investor can reach mutual consent through a direct agreement included in an investment contract. However, an impressive number of investment laws and investment treaties implement a process which allows private complainants direct access to arbitration against a State and public authorities based on an offer contained in those instruments. Scholars observed that through these new types of investment laws and investment treaties we have entered the era of arbitration without a contractual relationship between the parties to the dispute—or arbitration without privity. Although this has been seen as nothing short of a revolution of (traditional) arbitration theory, which postulates that arbitration is the product of a contract—either an arbitration clause for future disputes (p. 325) or an arbitration agreement for existing disputes—investment arbitration is nevertheless a consensual and contractual dispute resolution mechanism.

15.22  In fact the contractual arrangement should be understood broadly, in the sense that the parties’ consent can be given in different ways and successively.26 Thus, while in investment arbitration—based on an investment treaty or a national investment law—there is no arbitration agreement in the traditional sense, the arbitrators’ jurisdiction nevertheless stems from the initial consent of the State or public entity (expressed in the signing of the investment treaty or in the national investment law) and the subsequent consent of the claimant, who accepts the arbitrator’s jurisdiction by starting the arbitration.27 It has been observed that this implies consent more than requiring an express and specific manifestation of it. However, although there is no arbitration agreement in the traditional sense, the resolution of a dispute by private judges without the parties’ consent would not be arbitration.

15.23  The contractual nature of arbitration does not entail that the arbitration agreement must be ‘reciprocal’, ie give the parties the same right to refer disputes to arbitration.28 Indeed, it is possible to confer upon one party the unilateral29 right to initiate an arbitration proceeding.30 Notwithstanding these particularities, in investment arbitration—like in commercial arbitration—the attempt to emancipate arbitration from a State justice system is clear und unavoidable.31

15.24  While the expression of consent by instituting the arbitration proceeding (expression of consent by performance) is typical for investment arbitration and leads to an arbitration agreement which is a unilateral contract, there are also cases in investment arbitration where the foreign investor can express his consent to arbitration (acceptance) by promise.32 In the latter case the arbitration agreement is a bilateral contract.

15.25  For both commercial arbitration and investment arbitration, the determination of which law governs the validity of the arbitration agreement is of particular importance. In commercial arbitration this question is of importance because of the different solutions—traditional conflict of laws approaches, substantive rule of private international law or the French solution—adopted by national legislators for the formal validity of arbitration agreements and for determining the law governing the substantive validity of the arbitration agreement.33 In investment arbitration the issue is about whether the interpretation has to be done according to international law or national law.34 In both—commercial arbitration and investment arbitration—the question then arises about the inclination in interpreting the parties’ consent: shall it be interpreted in a restrictive, in an extensive, or in a neutral way?35

15.26  In commercial arbitration, due to technological evolution and a growing complexity of the cases, a relaxation of the form requirements took place.36 In investment arbitration issues with regard to form requirements arise primarily because of the way in which the host State expresses (p. 326) its consent to arbitration, ie through provisions contained in national investment laws or through provisions contained in investment treaties.37

5.  The scope perspective

15.27  In commercial arbitration most arbitration agreements are broadly worded, and, usually, when parties agree to resolve any disputes between them by arbitration, they intend to resolve all disputes between them by this method (unless a specific exception is made). This is particularly the case when the parties choose model clauses. Indeed the various arbitration institutions recommend model clauses with broad wording.38

15.28  Through the broad wording the parties agree that a bigger number of disputes fall within the scope of the arbitration agreement. However, as consent is expressed by the parties before the disputes break out, there is at the same time a reduction in the pure consensual character of arbitration. The enlargement of the scope of arbitration’s consent—because of a broad wording of the arbitration agreements—coupled with the reduction in the pure consensual character of arbitration—because consent to arbitration is expressed in advance—has been labelled the ‘paradox of consent’.39

15.29  In investment arbitration it is the host State’s offer which circumscribes the scope of consent to arbitration. The offer may vary. In ICSID arbitration Article 25 of the ICSID Convention defines the outer limits of the offer that the State parties may express. On the other hand there is nothing which can prevent States circumscribing offers in a narrower way. Although the scope of many investment treaties is broad, others limit their scope. The NAFTA and the ECT, for instance, both restrict the possible claims to violations of the treaties themselves. Limitations are also to be found in national investment laws. The foreign investor can accept or reject the offer of the host State to arbitration, but not limit or enlarge the host State’s offer. Indeed, a modification of the host State’s offer would be tantamount to a counteroffer.40

15.30  In commercial arbitration counterclaims are possible as long as they are covered by the arbitration agreement. Arbitration rules do not usually contain restrictions on the admissibility of counterclaims raised in the statement of defence.41 In the absence of a particular rule in the national arbitration laws or the chosen arbitration rules or procedural rules, the arbitral tribunal may determine the admissibility of counterclaims by virtue of its power to determine the arbitration proceedings.

15.31  International tribunals have generally affirmed their jurisdiction to hear counterclaims even when their constitutive instruments do not confer upon them an express power to do so. In investment arbitration where the contracting State parties have consented to investor–State arbitration in broad terms, in principle the possibility of counterclaims by the host State should therefore be given. On the other hand, the situation is less clear where consent is expressed in narrow terms, such as in the NAFTA.42

6.  The enlargement perspective

15.32  Consent to arbitration can also be analyzed under the viewpoint of a tendency to enlarge the reach of jurisdiction.

15.33  In commercial arbitration the question is mainly about the involvement in arbitration proceedings of third parties. On the one hand, it is generally accepted that a party may be (p. 327) introduced in arbitration through specific theories of contract law and general principles of corporate law, for instance agency, assignment, subrogation, third party beneficiaries, and universal succession. In all these cases the party that is not designated in the arbitration clause will not, strictly speaking, be a third party.43

15.34  On the other hand, arbitration agreements, like any substantive contract, can be ‘extended’ on a non-signatory party on the basis of consent implied by conduct. Non-signatory theories—in particular the doctrine of arbitral estoppel and the group of companies doctrine—have been developed and employed to facilitate deduction of consent to arbitrate implied by conduct.44 Indeed the main purpose of non-signatory theories is:

to presume or at least facilitate the deduction of consent. For example, in the context of the group of companies doctrine it can be enough for a party to prove that several companies constitute an ‘economic unit’ and that the non-signatory company has taken an ‘active role in the negotiation or the performance of the contract containing the arbitration agreement’ for the tribunal to presume the ‘common will of the parties to arbitrate’. In some cases non-signatory theories have gone as far as to suggest that mere awareness of the existence of an arbitration clause will be sufficient for a party to be bound by it.45

However, the acceptance to imply consent by conduct differs from jurisdiction to jurisdiction and scholars also have different views.

15.35  In investment arbitration the enlargement perspective is related to the jurisdictional requirements. With regard to the jurisdiction ratione personae the ICSID Convention itself provides for an enlargement of jurisdiction with Article 25(2)(b) which deals with the juridical persons that are incorporated in the host State but are controlled by nationals of another State. The main issue with this provision is what is meant by the concept of ‘foreign control’. In a pyramid of control the issues below may be controversial:

  • •  Which is the relevant party for the control?

  • •  How is control to be exercised?

  • •  How much control is necessary?

15.36  The ascertainment of ‘foreign control’ is not an easy task. The difficulties are mainly due to the fact that different criteria may find application in defining the concept of ‘foreign control’ in national investment laws and investment treaties and in interpreting it. Moreover there is an area of conflict between economic reality and legal structure. In addition, with regard to the relevant party for the control, the arbitral tribunal of the TSA Spectrum v Argentina case underlined the inconsistent case law.46

15.37  With regard to jurisdiction ratione materiae the fact that the concept of ‘investment’ is not defined by the ICSID Convention permits an enlargement of the limits upon the parties’ ability to consent to ICSID arbitration. Through the broad interpretation of the concept of ‘investment’, and the ‘subjectivist movement’, which attaches greater importance to the will of the parties in defining an economic operation as an investment, consent to arbitration experiences an expansion. However, while a broad interpretation stresses rather the jurisdictional side of arbitration, and normally goes to the ‘advantage’ of one of the parties, the ‘subjectivist movement’ underlines the contractual side of arbitration by taking into account the will of both of them.47

(p. 328) 15.38  In relation to jurisdiction ratione temporis the relevant date for determining whether the jurisdictional requirements are satisfied is the date of the institution of proceedings.48 However, the host State’s consent to arbitration normally also extends to investments that existed prior to the entry into force of the investment treaty.49 Moreover, disputes may also have begun prior to the entry into force of the investment treaty. Yet there are investment treaties that limit consent to arbitration to disputes arising after their entry into force. In that case, how ‘dispute’ is defined becomes fundamental. Arbitral tribunals have from time to time made a distinction between contract claims and treaty claims, or distinguished between divergences and disputes. In doing so they have been able to affirm jurisdiction.50

15.39  Another technique found in investment treaties, which may extend the scope of their protection, is the so-called ‘umbrella clause’. With umbrella clauses an expansion of the treaty’s consent to arbitration takes place by elevating contractual disputes to treaty disputes. The most contentious issue with regard to umbrella clauses is whether, and under what circumstances, they place investment agreements under treaty protection. Indeed the wording of umbrella clauses is not uniform. Consequently, the main factor affecting the host State’s consent to arbitration is the interpretation of umbrella clauses. Moreover, not all investment treaties contain umbrella clauses.51

15.40  Most arbitral tribunals have held that MFN clauses cannot prevail over the fundamental arbitration requirement—which is the meeting of the consent to arbitrate. MFN clauses therefore cannot be used to replace, in whole or in part, or to extend the dispute resolution mechanism provided in the investment treaty upon which jurisdiction is based. Nevertheless MFN clauses can be used to overcome waiting periods and comparable admissibility requirements.52

7.  The procedural needs perspective

15.41  Procedural needs may come into conflict with the consensual nature of arbitration. On the other hand, parallel proceedings leading to conflicting arbitral awards should be avoided. This is particularly true in investment arbitration where the same State’s measure may affect more people and in ICSID arbitrations where the possibilities of review are limited, because conflicting arbitral awards escape any further remedy by national courts.

15.42  Consolidation of proceedings and joinder/intervention of third parties in international arbitration have generally been possible only where the parties have unanimously agreed to such a result directly in their arbitration agreements, or indirectly by adopting arbitration rules which provide for consolidation of proceedings and/or joinder/intervention of third parties. Where the parties have not unanimously consented, national laws usually do not permit consolidation of proceedings or joinder/intervention of third parties. Some investment treaties also provide for the possibility of consolidation of proceedings.

15.43  In commercial arbitration in cases where arbitration rules provide for joinder and consolidation provisions—for instance the Swiss Rules—the disputing parties express their consent to arbitrate in the case of joinder and consolidation indirectly by adopting the rules.53 The new ICC Rules (2012) also contain provisions on joinder of additional parties and consolidation of arbitrations. However, according to the ICC Rules all parties must have consented to, or be (p. 329) bound by, the same arbitration agreement. Moreover, consolidation is also possible when the arbitrations are between the same parties. The ICC Rules therefore follow a strict consensual approach, ie indirect consent is not sufficient.

15.44  The national laws dealing with consolidation have adopted different solutions. Some national laws—for instance the English Arbitration Act 1996—do not really allow for consolidation without the express consent of the parties. Other national laws—for instance the Netherlands CCP—allow the courts to compel consolidation. In the latter cases it is less clear whether the parties have consented to consolidation, even though it might be argued that they have done so by choosing the seat of arbitration.

15.45  In investment arbitration the NAFTA, North American Model BITs, and free trade agreements concluded by the United States and Canada contain provisions allowing for consolidation of parallel proceedings. Where in investment arbitration the arbitral tribunal has discretionary power to order consolidation, it might be questioned whether the disputing foreign investor really has expressed his consent to have his proceedings arbitrated with the proceedings of another foreign investor.54

B.  The Consensual and Contractual Nature of Arbitration

15.46  The different perspectives under which the phenomenon of ‘consent in international arbitration’ has been resumed clearly show the complexity of the consensual nature of arbitration. Consent is not a dogma which should be abandoned.55 Rather the qualification of arbitration as a ‘consensual’ dispute resolution mechanism needs to be differentiated and reconciled with the jurisdictional side of arbitration.

15.47  To speak of marginalization of consent is also risky, because it gives the impression the importance of consent is declining. On the other hand this observation has the merit of reminding us that the jurisdictional side should not be forgotten. Indeed arbitration should ‘be reconciled with its jurisdictional side, which is as important and practically relevant as its contractual nature.’56 In other words, as it is not fully settled whether arbitration is of a contractual, jurisdictional, or mixed nature, one should not unduly favour the contractual over the jurisdictional element.57

15.48  The idea of a modern approach to consent58 is a very useful one, because it shows that an evolution has taken place. However, it is rather arbitration as a dispute resolution mechanism and its consensual nature which have evolved, whereas the concept of consent has adapted to this evolution. Indeed, with the appearance of complex multiparty situations and investment arbitration the face of arbitration and its consensual nature has undergone a process of transformation. Moreover the idea of a modern approach to consent suggests the complexity of the term ‘consent’ which is a polymorph term.

15.49  Finally the view that, in the case of investment arbitration, arbitration is a consensual but not a contractual dispute resolution mechanism59 should be rejected. While the terms ‘consensual’ and ‘contractual’ are not congruent, between a host State and a foreign investor an arbitration agreement is concluded when the foreign investor accepts the host State’s offer. The foreign investor’s acceptance can be by promise or by performance. In the former case, the arbitration (p. 330) agreement will be a bilateral contract and in the latter a unilateral contract. However, in both cases, host State and foreign investor are bound by a contract, as was rightly held by the English Court of Appeal60 and the US Court of Appeals for the Second Circuit.61 This view is also shared by eminent public international scholars.62

15.50  When the contractual viewpoint is consequently followed in the field of investment arbitration, it can provide interesting explanations for issues that arise with regard to limitations in the acceptance by the investor,63 to counterclaims,64 and to the irrevocability of host States’ offers.65

15.51  On the other hand, what is always to be remembered is that—contrarily to the term ‘contract’—the term ‘consent’ is a polymorph term. It may have the meaning of the unilateral expression of consent or the meaning of the mutual reach of consent. The mutual reach of consent is the substantive side of a contract. When the parties agree to arbitrate, they reach mutual consent and—when the other conditions are also fulfilled—conclude a contract called arbitration agreement. Therefore arbitration is a consensual and contractual dispute resolution mechanism.


1  On party autonomy see paras 2.04 et seq.

2  On the classical characterization of arbitration see Section A of Chapter 2.

3  On the historical evolution of the concept and the consensual nature of arbitration see Section B of Chapter 2.

6  Hanotiau, Consent, pp 539 and 554. On the discontent with the classical characterization of arbitration, in particular with its consensual nature, see paras 2.17 et seq.

7  Diallo. See paras 4.58 et seq.

8  On the multiple facets of consent to arbitration see Chapter 5.

9  On the proposal for a classification of types of consent see Section D of Chapter 5.

10  On the definition and types of arbitration agreements see paras 5.45 et seq.

11  On the framework of instruments where acceptance of the use of arbitration as a dispute resolution mechanism is embedded see Section C of Chapter 2.

12  On objective arbitrability see Section C of Chapter 3.

13  On the abolishment of the restrictions on States’ entitlement to enter arbitration agreements (subjective arbitrability) see Section B of Chapter 3.

14  On the expression of consent by the host State in investment arbitration see Section C of Chapter 11.

17  On consent to arbitration with a perceived reduced consensual character see Chapter 8.

18  On these instruments see Section C of Chapter 11.

19  See paras 2.54 and 2.56.

20  On consent to investment arbitration from a time perspective see Section D of Chapter 11.

21  On this view of investment treaty arbitration see paras 4.45 et seq.

22  See in general for contract law Beale, Bishop, and Furmston, p 208.

23  On consent to arbitration as expression of consent to arbitration or as reaching of mutual consent see Sections B and C of Chapter 5.

24  On the essential elements of consent to arbitration see paras 6.54 et seq.

25  On other important elements of consent to arbitration see paras 6.59 et seq.

29  On unilateral arbitration, see, eg Prujiner.

32  See, eg Art 8(3) of the UK Model BIT (2005), Preferred version.

33  On the laws governing the formal and the substantive validity in commercial arbitration see Section A of Chapter 6.

34  On the applicable law and interpretation in investment arbitration see Section A of Chapter 12.

35  On the inclinations in interpreting see for commercial arbitration paras 7.36 et seq and for investment arbitration Section B of Chapter 12.

36  On the relaxation of the form requirements in commercial arbitration see paras 6.41 et seq.

37  On the formal requirement of consent in investment arbitration see Section A of Chapter 11.

38  On the broadly worded arbitration agreements see paras 7.05 et seq.

39  On the ‘paradox of consent’ see para 7.09.

40  On the scope of consent and its limitations in investment arbitration see Section A of Chapter 14.

41  On counterclaims in commercial arbitration see paras 7.24 et seq.

42  On counterclaims in investment arbitration see Section B of Chapter 14.

43  On the extension of consent to arbitration by application of general principles of contract law or corporate law see Section A of Chapter 9.

44  On the extension of consent to arbitration to non-signatories see Section B of Chapter 9.

46  TSA v Argentina, Award, 19 December 2008, para 148. On consent in relation to jurisdiction ratione personae see Section C of Chapter 13.

47  On consent in relation to jurisdiction ratione materiae see Section B of Chapter 13.

48  On consent in relation to jurisdiction ratione temporis see Section D of Chapter 13.

49  See paras 13.123 et seq.

50  See paras 13.126 et seq.

51  On umbrella clauses see Section E of Chapter 12.

52  On MFN clauses see Section C of Chapter 14.

53  On joinder and intervention of third parties and consolidation of arbitration proceedings in commercial arbitration see Chapter 10.

54  On consolidation of arbitration proceedings in investment arbitration see Section E of Chapter 13.

59  Diallo.

60  Republic of Ecuador v Occidental Exploration and Production Co [2005] EWCA Civ 1116, paras 32–33 (Lord Phillips of Worth Matravers MR, Clarke, Mance LJJ).

61  Republic of Ecuador v Chevron (2d Cir 17 March 2011).

62  See, eg Crawford and Schreuer.

63  See paras 14.10 et seq.

64  See paras 14.13 et seq.

65  See paras 11.130 et seq.