Is the People’s Good the Highest Law? The Concept of Necessity in Investor-State Protections
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In April 2020, the Swedish telecommunications agency invited network operators to participate in a 5G network auction. The tender documents required bidders not to use equipment provided by the Chinese telecommunications giant Huawei. In excluding Huawei equipment from its 5G network, Sweden joined a long line of other nations. Countries that have issued partial or full bans on the use of Huawei equipment include Australia, France, Germany, New Zealand, the United Kingdom and the United States.
In each case, the stated reason for the ban was the same: that allowing the Chinese company to build national communication networks would imperil national security by giving the Chinese state a back door into those networks. Such concerns were heightened by China’s 2017 National Intelligence Law, which requires Chinese companies to cooperate with the state in national intelligence work. But Huawei has a different perspective: it sees the actions of Western governments as an attempt to stifle competition as part of a broader pushback against increasing Chinese economic power and political influence.
Unsurprisingly, Huawei has deployed investment claims, and the threat of such claims, as part of its response to these bans. On 7 January 2022, Huawei issued a request for arbitration under the China–Sweden bilateral investment treaty alleging that Swedish policy was ‘blatantly discriminatory’, a breach of the treaty’s fair and equitable treatment standard, and represented an expropriation of Huawei’s investments. Huawei has also issued a notice of dispute against the Czech Republic.
Huawei’s troubles illustrate the challenges facing the investment regime. The dramatic growth in investment disputes over the past 30 years was against the backdrop of ever-increasing globalisation. However contested its effects, the fact that the world was growing ever more interconnected was, until recently, largely taken as a given. This belief formed a core part of the ideological underpinnings of the investment regime. Now, it is clear that the tide runs swiftly in the opposite direction. Rising powers challenge the old Western-led order and states increasingly intervene in trade and economics to protect their national interests and to further political, social and economic goals. Against this backdrop, it is unsurprising that states are willing to invoke alleged national security interests to justify increased economic interventions.
This article focuses upon the legal status of such interventions. In particular, it considers the customary international law defence of necessity (the necessity defence), under which states may defend their actions on the basis that they are necessary to safeguard an essential interest. It also considers the relationship of that rule of customary international law with specific treaty provisions permitting states to take measures to protect their ‘essential security interests’ (ESI clauses).
The origins and nature of the necessity defence in Customary International Law
States have long invoked a defence of necessity. In 1837, in the ‘Caroline Affair’, pro-independence Canadian rebels fleeing British forces took refuge in American territory. In response, British forces entered American territory and attacked a ship owned by US citizens that was carrying the rebels. Faced with American protests, Britain justified its conduct on grounds of necessity. In response, the United States took the position that such a defence would only be engaged where the ‘necessity of self-defence was instant, overwhelming, leaving no choice of means and no moment of deliberation’. Before the Second World War, states invoked necessity as a justification for the issue of prohibitions on seal hunting to prevent the imminent extinction of a seal population (as in the Russian Fur Seals dispute), as a justification (albeit unsuccessfully) for non-payment of the Ottoman Empire’s sovereign debt to Russia (in the Russian Indemnity case), and as a justification for non-payment of arbitral awards (in Société commerciale de Belgique), among other invocations of the principle.
The customary international law on necessity is embodied in Article 25 of the Draft Articles on Responsibility of States for Internationally Wrongful Acts (the Draft Articles).
Article 25 provides that:
1. Necessity may not be invoked by a State as a ground for precluding the wrongfulness of an act not in conformity with an international obligation of that State unless the act:
(a) is the only way for the State to safeguard an essential interest against a grave and imminent peril; and
(b) does not seriously impair an essential interest of the State or States towards which the obligation exists, or of the international community as a whole.
2. In any case, necessity may not be invoked by a State as a ground for precluding wrongfulness if:
(a) the international obligation in question excludes the possibility of invoking necessity; or
(b) the State has contributed to the situation of necessity.
The International Court of Justice (ICJ) has held necessity, as formulated in an earlier version of the Draft Articles, to be a defence recognised in customary international law. Equally, investment tribunals have treated the Draft Articles as reflecting the state of customary international law in relation to the doctrine of necessity.
The International Law Commission made clear that it considered that the defence of necessity should only be invoked to preclude international wrongfulness in exceptional circumstances. For this reason, it adopted a ‘negative’ formulation of the defence, intended to show that this was an exceptional defence and ‘one more rarely admissible than is the case with the other circumstances precluding wrongfulness’. That negative formulation mirrors the language of Article 62 of the Vienna Convention dealing with termination of treaties for fundamental change of circumstances.
Application of the necessity defence
It should be recalled that the Draft Articles are intended to be a reflection of customary international law. They are not a treaty and should not be subjected to a process of semantic interpretation. However, in practice the requirements of Article 25 can be distilled into the following elements that must be demonstrated by the invoking state:
- the measures must be to safeguard an ‘essential interest’ of the state;
- they must be the only way of safeguarding that interest;
- the measures must address a ‘grave and imminent peril’;
- no other essential interest of the state, another state, or the international community should be seriously impaired as a result of the breach.
In addition, the defence will be unavailable if (1) the international obligation excludes the possibility of invoking necessity or (2) the state has contributed to the situation of necessity. The scope of these requirements have been considered by a number of investment arbitrations, most intensively by tribunals considering ‘pesification’ measures taken by Argentina in response to its 2001 financial crisis.
A number of investment tribunals have taken an extremely narrow view of what constitutes an ‘essential interest’ of a state in the context of the necessity defence, holding that an essential interest is only engaged where the situation compromises the very existence of the state and its independence. This is to be distinguished from a threat to the fortunes of a particular government or political party, which will not engage an essential interest.
A narrow approach to the construction of the ‘essential interest’ requirement has some support in the decision of the tribunal in the Russian Indemnities case, concerning the failure of the Ottoman Empire to pay war indemnities due to subjects of the Russian Empire following the Russo-Turkish War of 1877–1878. In that case, the tribunal rejected a defence of necessity (which was treated for the purposes of that case as synonymous with force majeure) on the basis that payment of the outstanding sums would not ‘imperil the existence of the Ottoman Empire’.
However, other adjudicatory bodies have questioned whether the ‘essential interest’ requirement should be so narrowly construed. The issue was addressed more fully by the ICJ in the Gabčíkovo-Nagymaros Project case, brought by Slovakia as a result of Hungary’s decision to suspend the construction of a major joint hydropower project on the Danube. Hungary’s stated reason for the project suspension was concern about the environmental risks associated with the project. Citing commentary of the International Law Commission, the ICJ held that concerns about protection of the natural environment could amount to an ‘essential interest’, which was not confined solely to matters concerning the ‘existence’ of the state.
In Impregilo v Argentina, the investment tribunal held that ‘the term “essential interest” can encompass not only the existence and independence of a State itself, but also other subsidiary but nonetheless “essential” interests, such as the preservation of the State’s broader social, economic and environmental stability . . . and its ability to provide for the fundamental needs of its population.’ Likewise, in AWG v Argentina, the provision of water supplies was held to be vital to the health and wellbeing of nearly 10 million people and therefore an essential interest of the Argentine state.
The only way?
The Draft Articles provide that the necessity defence cannot succeed if there are other lawful means of safeguarding the essential interest of the state. The International Law Commission’s Commentary states that it does not matter if such means are more costly or less convenient than the measures ultimately adopted.
As the International Court of Justice made clear in the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory case, this requirement of Article 25 must be strictly applied even in the face of the gravest circumstances. While the ICJ recognised in that case that ‘Israel ha[d] to face numerous indiscriminate and deadly acts of violence against its civilian population’ and had the duty to respond in order to protect the life of its citizens, ‘[t]he measures taken are bound nonetheless to remain in conformity with applicable international law’, and the court was ‘not convinced that the construction of the wall . . . was the only means to safeguard the interests of Israel’.
The tribunal in CMS held that the measures adopted by Argentina, were not the ‘only’ steps available. For their part, the tribunals in Enron and Sempra held that a comparison ‘shows that there are always many approaches to address and correct such critical [economic] events’, and it is difficult to establish that none of them were available in the Argentine case. Both tribunals further held that it was not their task to determine whether one approach would have been better than the other, but simply to ‘determine whether the choice made was the only way available’.
Even the decision in LG&E, which granted Argentina’s necessity defence for a temporary period, stated that the ‘only way’ requirement in Article 25(1)(a) implies ‘that it has not been possible for the State to avoid by any other means, even a much more onerous one that could have been adopted and maintained the respect of international obligations.’ According to the LG&E tribunal, ‘[t]he State must have exhausted all possible legal means before being forced to act as it does.’
Grave and imminent peril
The Draft Articles provide no definition of what constitutes a ‘grave and imminent peril’. However, commentary upon this requirement is found in the Gabčíkovo-Nagymaros Project case, in which the ICJ held that:
a state of necessity could not exist without a ‘peril’ duly established at the relevant point in time; the mere apprehension of a possible ‘peril’ could not suffice in that respect. It could moreover hardly be otherwise, when the ‘peril’ constituting the state of necessity has at the same time to be ‘grave’ and ‘imminent’. ‘Imminence’ is synonymous with ‘immediacy’ or ‘proximity’ and goes far beyond the concept of ‘possibility’. As the International Law Commission emphasized in its commentary, the ‘extremely grave and imminent’ peril must ‘have been a threat to the interest at the actual time’ […]. That does not exclude, in the view of the Court, that a ‘peril’ appearing in the long term might be held to be ‘imminent’ as soon as it is established, at the relevant point in time, that the realization of that peril, however far off it might be, is not thereby any less certain and inevitable.
On the facts in that case there was no ‘grave and imminent peril’ as at the time of the relevant measures, the peril of environmental damage remained uncertain. However, the decision is important in recognising that a risk may still be ‘imminent’ even if it may not eventuate for some time, provided that the risk is sufficiently certain.
Investment tribunals have generally dealt lightly with this requirement. In Sempra and Enron v. Argentina, the tribunal considered that the requirement was not satisfied because ‘there is no convincing evidence that the events were out of control or had become unmanageable’.
If accepted more widely, the test of unmanageability articulated in Enron would seriously circumscribe the operation of the necessity defence. It is difficult to imagine that many (or any) cases of temporally remote risks, such as those considered in the Gabčíkovo-Nagymaros Project case would satisfy such a test.
Article 25(1)(b) of the Draft Articles provides that the measures must not impair the essential interest of the state or states towards which the obligation exists or of the international community as a whole. The language of the Draft Articles is not directly tailored to the investor–state context, in which there is a third party, the investor, who also has interests protected by the relevant treaty. Is the protection of the interests of investors an ‘essential interest’ of the contracting states, such that it cannot be disregarded even to safeguard an essential interest?
In CMS, the tribunal held that while the protection of investors was an ‘important’ interest of the state parties, it did not rise to the level of an ‘essential interest’ such that the plea of necessity would be precluded. The tribunal did not offer any detailed justification for this view but without such a conclusion, either explicitly or implicitly, it is difficult to see how the necessity defence could ever successfully be invoked in the investor–state context.
Exclusion of the necessity defence
Under Article 25(2)(a) of the Draft Articles, the necessity defence may not be invoked if ‘the international obligation in question excludes the possibility of invoking necessity’. The exclusion can be express or implicit in the nature of the treaty. The classic example of such an exclusion would be where the treaty is designed specifically to apply in circumstances of necessity (for example, treaties governing humanitarian rules for armed conflict), in which case the nature of the treaty will exclude the necessity defence.
In general, bilateral investment treaties are silent on the necessity defence, meaning that there is no direct textual basis for arguments as to whether the defence has been excluded. However, the defence may be excluded even absent express wording where the relevant measures contravene one of the state’s general international obligations. For example, in Border Timbers, the tribunal held that even absent express treaty language dealing with necessity, Zimbabwe had contravened its international legal obligations erga omnes by engaging in racial discrimination, meaning that it had failed to satisfy this requirement for invoking necessity.
If the state has contributed to the situation of necessity then it cannot rely upon the necessity defence. But what constitutes a ‘contribution’? The commentary on the Draft Articles states that ‘the contribution to the situation of necessity must be sufficiently substantial and not merely incidental or peripheral.’ Assessing whether a contribution is sufficiently substantial can lead tribunals into difficult areas of political and economic appraisal. As the tribunal in Mobil v. Argentina recognised, economics is not an exact science lending itself to ready appraisal of matters of causation. Despite this, the majority of the tribunal was still willing to find that Argentina had contributed through its economic policies to its financial crisis. Such a substantial contribution could still be found even if there are significant exogenous causes of the crisis as well.
In Impreglio, the tribunal considered whether mere negligence could amount to a contribution, holding that the state’s contribution to the crisis need not be specifically intended or planned – it could be the consequence of ‘well-intended but ill-conceived policies’. As in Mobil, the tribunal considered that Argentina’s long term failure to exercise fiscal discipline made it vulnerable to crisis and amounted to a sufficiently significant contribution to the situation of necessity.
As the summary set out above demonstrates, states seeking to invoke the necessity defence face formidable obstacles. It is therefore unsurprising that such states often seek to rely instead upon their negotiated treaty exemptions, to which we now turn.
ESI clauses distinguished from the necessity defence
It is important to distinguish the necessity defence from the non-precluded measures clauses that form a common feature of investment treaties. Such clauses provide that certain actions taken in pursuit of particular national economic or social interests will not represent a violation of the treaty. A subset of such clauses is the ESI clause, which ties the permitted measures to the objective of protection of security interests. In the case of states that have taken measures in respect of Huawei, such a clause is found, for example in Article 11 of the China–New Zealand Bilateral Investment Treaty.
Such clauses create a potential interaction with the necessity defence by invoking similar principles of essential state interests. Interaction between such clauses and the necessity defence has been a contentious issue. This is well illustrated by the Argentina cases, each of which was brought under the US–Argentina BIT, whose Article XI provided that:
This Treaty shall not preclude the application by either Party of measures necessary for the maintenance of public policy, the fulfilment of its obligations with respect to the maintenance or restoration of international peace or security, or the Protection of its own essential security interests.
For the CMS, Enron and Sempra tribunals the concept of ‘necessity’ employed in Article XI of the BIT fell to be interpreted through the lens of the requirements for necessity articulated in customary international law. As discussed above, this resulted in a highly restricted reading of the circumstances in which a plea of necessity could be employed and consequently, on those tribunals’ approach, greatly circumscribed the application of Article XI.
In contrast, the Annulment Committee in CMS considered that the tribunal had made an error of law by treating Article XI and the necessity defence as the same, albeit it considered that it would exceed the Annulment Committee’s jurisdiction to annul the award on that basis. Likewise, in Continental Casualty, the tribunal observed that such an essential security clause was conceptually distinct from the customary international law necessity defence in a number of ways:
- While the necessity defence operated as a defence to state responsibility, Article XI, if satisfied, functioned as a defence to any wrongdoing. If Article XI applied, there would be no treaty violation at all.
- While the customary international law defence was considered by the tribunal to only apply on an exceptional basis and subject to strict conditions, reflecting the fact that the defence could be invoked in any circumstances against any international liability. In contrast, the tribunal considered that the bilaterally agreed requirements of Article XI were ‘not necessarily’ subject to the same conditions of application.
Based on this line of analysis, the annulment committee in Sempra annulled the Sempra award for containing a manifest error of law that amounted to an excess of powers because it considered that the tribunal had adopted the wrong applicable law by applying Article 25 of the Draft Articles in preference to Article XI of the treaty.
If that approach is correct, the question then becomes how do the requirements to engage an ESI clause differ from those of the necessity defence? Ultimately, this will be a matter of the proper construction of the particular treaty provision. That different clauses can produce very different outcomes is illustrated by the outcomes of the recent CC/Devas and Deutsche Telekom cases against India. Both of those cases concerned the termination of a contract with an Indian state entity allowing the claimant to make use of satellite spectrum. However, the claims were brought under different treaties:
- In CC/Devas, the claim was brought under the India–Mauritius treaty, which provided that the state’s actions needed to be ‘directed to the protection of’ its essential security interest.
- In Deutsche Telekom, the India–Germany treaty’s ESI clause applied to decisions that were ‘necessary’ to protect that interest.
While based on very similar underlying facts, the tribunal in CC/Devas held that the ESI clause was engaged, while the Deutsche Telekom tribunal found that it was not.
Despite the impact of treaty language, there are certain general principles that can be derived from the cases, which are discussed below.
Scope of the essential interests
In the context of an ESI clause, the interest covered by such clauses may be expressly tied by the drafting of the clause to specified interests, most commonly a state’s military or defence interests. Where the clause is drafted in more general terms, it is strongly arguable that the range of essential interests can be construed more broadly to encompass the economic security of the state and its population.
While it seems clear that military interests can engage the state’s essential interests, the type of military interests that would rise to the level of being essential is less clear. The CC/Devas v. India and Deutsche Telekom v. India cases both arose against the background of India’s cancellation of a contract for provision of telecommunications spectrum. That measure was said to be justified on the basis that the spectrum was needed to meet the communications needs of India’s military. Both the tribunals concluded, without detailed analysis, that in principle the strategic need for communications bandwidth represented an essential interest.
In contrast, both tribunals agreed that non-military interests such as the needs of public utilities would not amount to an essential security interest. Given the wider approach to definition of an essential interest under the necessity defence discussed above, such an approach would have the potential effect of making ESI clauses more restrictive than the necessity defence. That position contrasts with that reached in the jurisprudence of the ECJ in relation to the ‘public security’ exception under the TFEU.
Relevance of an ‘only way’ standard
In CMS, Enron and Sempra, the tribunals found that the ESI clause in those cases reflected the requirement under the necessity defence that the measures be ‘necessary’ to achieve the essential security interest means that such measures must be the ‘only way’ to do so.
In contrast, in Deutsche Telekom v. India, the tribunal held that the ‘only way’ requirement did not apply to an ESI clause. Instead, the question for the tribunal was whether ‘the measure was principally targeted to protect the essential security interests at stake and was objectively required in order to achieve that protection, taking into account whether the state had reasonable alternatives, less in conflict or more compliant with its international obligations’. On the facts, the tribunal held that India had not established that the measures were ‘necessary’ to protect the relevant security interests.
In CC/Devas, the tribunal had to consider an ESI clause that referred to measures that were ‘directed to’ an essential security interest, rather than being ‘necessary’ to achieve that interest. The tribunal held that this language suggested that there was no requirement to show ‘necessity’ in the sense that the measures in question were the only way to protect the relevant essential security interest. Instead, a more permissive standard applied, namely whether the measure related to the state’s essential security interest.
That conclusion highlighted one of the central difficulties in approaching ESI clauses, namely whether they are ‘self-judging’. In other words, to what extent is a tribunal entitled to review the state’s assessment that a particular measure is directed to an essential security interest. While ESI clauses are generally not treated as being self-judging, prior analysis had suggested that clauses such as that considered in CC/Devas ‘came very close to self-judging clauses’ subject only to the state’s general legal duty to exercise its treaty rights in good faith. The tribunal in CC/Devas was at pains to stress its deference to the state’s discretion:
An arbitral tribunal may not sit in judgment on national security matters as on any other factual dispute arising between an investor and a State. National security issues relate to the existential core of a State. An investor who wishes to challenge a State decision in that respect faces a heavy burden of proof, such as bad faith, absence of authority or application to measures that do not relate to essential security interests.
However, it concluded that such clauses were not truly self-judging because the security interests in question must be ‘essential’. Whether this requirement was met remained a matter for the tribunal’s assessment.
On any view, the threshold for establishing a necessity defence under customary international law is a high one, with the defence intended to operate in exceptional circumstances. As the cases set out above demonstrate, the jurisprudence on the scope and application of the necessity defence remains unsettled, with tribunals forced to make difficult calls on areas of economic and political strategy. Equally, the distinction between the necessity defence and ESI clauses has been potentially underappreciated. As the facts of CC/Devas illustrate, the ESI clause can provide a potentially more far ranging opportunity for states to argue that acts that would otherwise represent a treaty breach are permissible. That greater scope for defensive arguments comes though at the cost of increased uncertainty as to the meaning and availability of treaty protections.
The recent interventions in relation to Huawei also serve to illustrate how in a modern economy, the scope of activities that impinge upon a state’s security interests is potentially greater than ever before. If the preservation of satellite capacity for military uses represents an essential security interest, as in CC Devas and Deutsche Telekom, so is it at least arguable that the preservation of communications from potential espionage also falls within that rubric. Yet the essential problem of identifying the limits of the state’s right to intervene to protect its interests remains. Even on an expansive view of the state’s discretion, tribunals will still be called upon to make judgments as to the state’s priorities and available choices. Whether considered under the necessity defence or as a matter of the construction of an ESI clause, the world’s growing uncertainty suggests that those issues will not go away.
 David Hunt and Ben Love are partners and Gina Rossman is an associate at Boies Schiller Flexner (UK) LLP.
 Huawei Technologies Co., Ltd. v. Kingdom of Sweden (ICSID Case No. ARB/22/2), Request for Arbitration, 7 January 2022, Paras. 94–97.
 ‘Letter to Henry Stephen Fox’, in K.E Shewmaker (ed.). The Papers of Daniel Webster: Diplomatic Papers, vol. 1. 1841-1843 (1983) 62.
 Award between the United States and the United Kingdom relating to the rights of jurisdiction of United States in the Bering’s sea and the preservation of fur seals, Decision of 15 August 1893.
 Russia v. Turkey ( 1911 ) 11 R.I.A.A. 421.
 Société commerciale de Belgique, Judgment, 1939, P.C.I.J., Series A/B, No. 78, p. 160.
 Gabčíkovo-Nagymaros Project (Hungary/Slovakia), ICJ Judgment, 25 September 1997, Para. 51. In this case the ICJ considered an earlier version of the Draft Articles, which pre-dated the International Law Commission’s second reading of the Draft Articles. In that version, the provisions on necessity were found in Article 33 and were substantially the same as in Article 25, save for inclusion of an additional express exemption to the defence for acts contrary to peremptory international norms.
 See, e.g., Sempra Energy International v. Argentine Republic, ICSID Case No. ARB/02/16, Award, 28 September 2007, Para. 344.
 Yearbook of the International Law Commission, 1980, Vol II, Part 2, Para. 40; see also Commentary to the Draft Articles p. 85.
 See Enron Creditors Recovery Corporation (formerly Enron Corporation) and Ponderosa Assets, L.P. v. Argentine Republic, ICSID Case No. ARB/01/3, Award, 22 May 2007, Para. 306; Sempra Energy International v. The Argentine Republic, ICSID Case No. ARB/02/16, Award, 29 September 2007, Para. 348. However, in the Enron annulment proceedings, the Annulment Committee found that the tribunal had in fact left open the question of what constituted an essential interest; Enron Creditors Recovery Corporation (formerly Enron Corporation) and Ponderosa Assets, L.P. v. Argentine Republic, ICSID Case No. ARB/01/3, Decision on the Application for Annulment of the Argentine Republic, 30 July 2010, Para. 359.
 Bernhard von Pezold and others v. Republic of Zimbabwe, ICSID Case No. ARB/10/15, Award, 28 July 2015, Para. 631.
 Gabčíkovo-Nagymaros Project (Hungary/Slovakia), Judgment, 25 September 1997, Para. 53.
 Impregilo S.p.A. v. Argentine Republic (I), ICSID Case No. ARB/07/17, Award, 21 June 2011, Para. 346.
 AWG Group Ltd. v. The Argentine Republic, Decision on Liability, 30 July 2010, Para. 260.
 Commentary to the Draft Articles, p. 83.
 Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, ICJ Rep. 2004, p. 3.
 ibid., Paras. 140–141.
 CMS Gas Transmission Company v. Argentine Republic, Para. 324.
 Enron, Para. 308; Sempra, Para. 350.
 Enron, Para. 309; Sempra, Para. 351.
 LG&E Energy Corp., LG&E Capital Corp. and LG&E International Inc. v. Argentine Republic, ICSID Case No. ARB/02/1, Decision on Liability, 3 October 2006, Para. 250.
 Gabčíkovo-Nagymaros Project (Hungary/Slovakia), Judgment, 25 September 1997, Para. 54.
 Enron Creditors Recovery Corporation (formerly Enron Corporation) and Ponderosa Assets, L.P. v. Argentine Republic, ICSID Case No. ARB/01/3, Award, 22 May 2007, Para. 307.
 CMS Gas Transmission Company v. Argentine Republic (ICSID Case No. ARB/01/8), Award of 12 May 2005, Para. 358.
 ibid., Para. 327.
 Border Timbers Limited, Timber Products International (Private) Limited, and Hangani Development Co. (Private) Limited v. Republic of Zimbabwe, ICSID Case No. ARB/10/25, Award, 28 July 2015, Para. 657.
 Commentary to the Draft Articles, p. 85.
 Mobil Exploration and Development Inc. Suc. Argentina and Mobil Argentina S.A. v. Argentine Republic, ICSID Case No. ARB/04/16, Decision on Jurisdiction and Liability, 10 April 2013, Para. 1124.
 See, for example, CMS Gas Transmission Company v. The Argentine Republic, ICSID Case No. ARB/01/8, Award, 12 May 2005, Para. 329.
 Impregilo S.p.A. v. Argentine Republic (I), ICSID Case No. ARB/07/17, Award, 21 June 2011, Para. 356.
 See, for example, Sempra Energy International v. Argentine Republic (ICSID Case No. ARB/02/16), Award of 28 September 2007, Para. 376: ‘the Treaty provision is inseparable from the customary law standard insofar as the definition of necessity and the conditions for its operation are concerned.’
 CMS Gas Transmission Company v. The Argentine Republic, ICSID Case No. ARB/01/8, Award, 12 May 2005, Para. 308, treating the interpretation of Article XI and the Necessity Defence as ‘one fundamental issue’; Sempra Energy International v. Argentine Republic, ICSID Case No. ARB/02/16, Award, 28 September 2007, Para. 376; Enron Creditors Recovery Corporation (formerly Enron Corporation) and Ponderosa Assets, L.P. v. Argentine Republic, ICSID Case No. ARB/01/3, Award, 22 May 2007, Para. 333.
 CMS Gas Transmission Company v. The Argentine Republic, ICSID Case No. ARB/01/8, Decision of the Ad hoc Committee on Argentina’s Application for Annulment, 25 September 2007, Para. 130.
 Continental Casualty Company v. Argentine Republic, ICSID Case No. ARB/03/9, Award, 5 September 2008, Para. 164.
 Continental Casualty Company v. Argentine Republic, ICSID Case No. ARB/03/9, Award, 5 September 2008, Para. 167. See also LGE v. Argentina, where the tribunal held that its conclusion that the requirements of Article XI were satisfied was supported by its conclusion that the requirements of the Necessity Defence were also made out, treating these as two separate but complementary analyses. LG&E Energy Corp., LG&E Capital Corp. and LG&E International Inc. v. Argentine Republic, ICSID Case No. ARB/02/1, Decision on Liability, 3 October 2006, Para. 245.
 Sempra Energy International v. Argentine Republic, ICSID Case No. ARB/02/16, Decision on the Argentine Republic’s Application for Annulment of the Award, 29 June 2010, Para. 208.
 In an ICSID case, such as that pending between Huawei and Sweden, interpretation of the ESI clause may also be assisted by the submission of amicus briefs by non-disputing parties, pursuant to Rule 37 of the ICSID Rules. Such briefs may be provided by other states whose treaties contain ESI clauses in support of the respondent’s interpretation of such clauses.
 For an insightful analysis of the ways in which the difference in decision is driven less by the language of the relevant treaties and more by the differing analytical approaches of the tribunals in those cases see R Kabra, ‘Return of the Inconsistent Application of the “Essential Security Interest” Clause’ in ‘Investment Treaty Arbitration: CC/Devas v India and Desutche Telekom v India’, ICSID Review 34(3) (2019).
 See, for example, Article XXI of the GATT, which refers to ‘traffic in arms, ammunition and implements of war and to such traffic in other goods and materials as is carried on directly or indirectly for the purpose of supplying a military establishment’.
 Continental Casualty Company v. Argentine Republic, ICSID Case No. ARB/03/9, Award, 5 September 2008, Para. 175.
 CC/Devas (Mauritius) Ltd., Devas Employees Mauritius Private Limited, and Telcom Devas Mauritius Limited v. Republic of India, Para. 354; DK Telekom v. India, Para. 284.
 Campus Oul v. Minister for Industry and Energy  3 CMLR 544.
 Deutsche Telekom AG v. India, PCA Case No. 2014-10, Interim Award, 13 December 2017, Para. 239.
 CC/Devas (Mauritius) Ltd., Devas Employees Mauritius Private Limited, and Telcom Devas Mauritius Limited v. Republic of India, PCA Case No. 2013-09, Award on Jurisdiction and Merits, 25 July 2016, Para. 243.
 See, e.g. Sempra Energy International v. Argentine Republic, ICSID Case No. ARB/02/16, Award, 28 September 2007, Para. 388.
 The protection of national security in IIAs, UNCTAD Series on International Investment Policies for Development (2009), p. 95.
 CC/Devas v. India, PCA Case No. 2013-09, Award on Jurisdiction and Merits, 25 July 2016, Para. 245.
 ibid., Para. 243.