Prof. Dr. Alexander Reuter *
The ECJ’s Achmea and CETA rulings ; as well as the entire debate conducted on the issue so far, disregard one legal factor, that is, the binding legal effect of investors’ rights under investment treaties. That factor is, however, at the heart of the matter and decisive. Under EU procedural law that factor can be raised at any time as a “fresh issue of law”. Thus, the Achmea and CETA rulings of the European Court of Justice do not bar intra-EU investment arbitration.
This proposition is not to contribute to the voluminous debate on Achmea and on the compatibility of intra-EU investment arbitration with TFEU art. 344, 267 and 18 or other EU governance principles such as the “principle of mutual trust”. In contrast, that proposition is based on investors’ rights under public international law as third parties, and the binding effect on the EU, its institutions and its member states of such rights. In addition, under the criteria developed by said ECJ rulings, intra-EU ISDS under the ECT fares better than the CETA.
The above propositions are set out in more detail by the author in the Heidelberg Journal of International Law (HJIL) (Zeitschrift für ausländisches öffentliches Recht und Völkerrecht; ZaöRV). 
A) Third party rights under public international law
In Achmea the European Court of Justice (”ECJ“) found intra-EU investment arbitration under the bilateral investment treatybetween Slovakia and the Netherlands to violate the principles of mutual trust and sincere cooperation amongst EU member states, the supremacy of EU law and the protection of the ECJ’s own competence to ensure the uniform application of EU law. All of these principles concern the internal governance of the EU, its member states and its institutions, not investors’ rights. On the other hand, in the last years a great many arbitral tribunals dealt with intra-EU investment arbitrations, most of them under the Energy Charter Treaty (“ECT”), a multilateral investment treaty to which the EU has acceded. None of these tribunals found the proceedings to be incompatible with EU law.  The tribunals refer to the general interpretation rules of the Vienna Convention on the Law of Treaties (VCLT) and, as one tribunal has worded it, a carve-out for intra-EU conflicts would be “incoherent, anomalous and inconsistent with the object and purpose of the ECT”, the rules of international law on treaty interpretation, in particular the universal recognition of “the principles of free consent and of good faith and the pacta sunt servanda rule”. 
This is in line with the intent of the EU institutions involved with the accession by the EU to the ECT. The internal documents preparing the accession demonstrate that the EU did not intend the ECT to distinguish between intra-EU and extra-EU disputes. In line therewith, the ECT, as adopted not only by all EU member states, but by both the European Commission and the European Council, does not contain any indication that differing rules should apply “intra-EU” on the one hand and in respect of non-EU parties on the other hand. In contrast, by a declaration made when acceding to the ECT (see Annex ID to the ECT)  , the European Communities did not only set forth that the “European Communities and their Member States” are “internationally responsible” for the fulfillment of the ECT, it also expressly mentions the “right of the investor to initiate proceedings against both the Communities and their Member States”. Additionally, the declaration expressly deals with the role of the ECJ and documents that the EU acceded to the ECT in full cognizance of the fact that the ECJ can be involved in such proceedings only (1) “under certain conditions” and in particular only (2) “in accordance with art. 177 of the Treaty” [now TFEU art. 267]. Hence, the declaration expresses the acceptance by the EU of the curtailment to the competences of the ECJ resulting from investment arbitration under the ECT.
B) Taking investors’ rights seriously: Their binding effect within the EU
The reason for this discrepancy between the findings of the ECJ and those of the arbitral tribunals can already gleaned from the above: While the tribunals deal with investors’ rights under the relevant investment treaties, the ECJ is concerned with intra-EU governance issues.  However, governance issues do not do away with the fact that investment treaties form part of public international law and bestow private investors with the rights (1) that the host state comply with the treaty’s protection standards and (2) to take the host state to arbitration. Such private enforcement is even one of the essential features of investment treaties.  Which consequences does this have within the EU?
Even the ECJ concedes that public international law treaties must be interpreted in accordance with the VCLT, notably “in good faith in accordance with the ordinary meaning to be given to its terms in their context and in the light of its object and purpose”. Thus, for purposes of public international law, the ECJ must be taken to recognize (1) that investment treaty rights vest with the investors and (2) the fact that all arbitral tribunals involved have affirmed the ECT, under public international law, to cover intra-EU investments. There is no indication that such a long, uniform and unequivocal line of arbitral holdings does not constitute an interpretation of the ECT “in good faith in accordance with the ordinary meaning to be given to its terms in their context and in the light of its object and purpose”.
In turn, under TFEU art. 216(2) “Agreements concluded by the Union are binding upon the institutions of the Union and on its Member States”. Admittedly, the ECJ makes an internal exception to TFEU art. 216 (2), that is, an exception as regards the parties to the EU Treaties, the EU and its institutions: Vis-a-vis these parties the ECJ confines the binding effect of treaties under art. 216 to supremacy over secondary EU law, and carves out primary EU law.  However, this internal limit to the effect of public international law treaties does not apply to third parties. Vis-à-vis third parties, under public international law the EU is bound by the treaties it has concluded.  The ECJ has held „that the Community cannot rely on its own law as justification for not fulfilling [the international treaty at bar].“  As private investors are third parties, this holds true for them as well, and all the more so as their means to analyse the internal governance rules of the EU (or a host state) for potential infringements which may impact the validity of the treaty or of obligations contained therein, are substantially lower than the means of the other state parties which negotiated, concluded, and agreed on the ratification process for, the relevant treaty. In short: Pacta sunt servanda, in particular where investors have made investments which they cannot undo. 
In this connection it is irrelevant that intra-EU investment arbitration is typically directed against the relevant host state, not against the EU. As a party to the ECT, the EU is bound not to obstruct the due implementation of the rights and obligations of investors and the relevant host states. In contrast, the obstruction by the EU of the due implementation of the ECT would constitute a treaty violation in itself. 
C) Consequences for Intra-EU bilateral investment treaties
The above considerations do not directly apply to bilateral investment treaties (“BITs”) between EU member states, to which the EU has not acceded. However, rights vesting under a BIT are not without protection under EU law either: First, where a host state has acceded to the EU after it has entered into a BIT, TFEU art. 351 grandfathers rights of investors as third parties. Second, there may have been acts or omissions of the EU in connection with the relevant treaty. Third, while, in general, determining EU law with retroactive effect, under its case-law the ECJ may be “moved” to carve-out “existing relationships” from such effect. 
Invoking investors’ rights is not precluded by a “precedent” character of Achmea or CETA: Preliminary rulings under TFEU art. 267 only bind the national court, and thus the parties, to the main proceedings in question  . Nevertheless, referral procedures under TFEU art. 267 have the purpose to have EU law interpreted for the EU as a whole and thus have a factual precedent effect.  However, the ECJ has confirmed the right to make a (further) reference on a “fresh question of law” or “new considerations which might lead the ECJ to give a different answer to a question submitted earlier”.  As a result, Achmea and CETA have no binding or precedent effect beyond the considerations they have dealt with.
These considerations do not include investors’ rights: Achmea, as already mentioned, is confined to EU governance issues. CETA, in contrast, did not fail to consider the position of investors. However, these were ex ante considerations, not the protection of investors who have already made investments in reliance on a treaty. It did thus not deal with a treaty which had already been concluded, had come into force, had bestowed rights on investors, and in reliance on which investors had made investments. 
In contrast, the ECT is a concluded treaty which has been in force for many years and under which investors have already made a great many intra-EU investments. Thus, when making their investments, investors were entitled to have the expectation that the ECT would be respected by its parties, including the EU.
E) Applying the criteria of the CETA Opinion
In the alternative: If one (contrary to the above) were to disregard investors’ rights under public international law, the question arises how the ECT would fare under the criteria selected by Achmea and CETA to assess the compatibility of intra-EU investment arbitration with EU law. A detailed analysis shows that the ECT does not run aful of, but meets, those criteria. 
F) A matter of justice
The conclusion is: Investors are entitled to rely on their investment treaty rights. Under public international law, the EU position regarding intra-EU ISDS is, as the Vattenfall tribunal has expressed it, “unacceptable”, “incoherent”, “anomalous and inconsistent”.  This is corroborated by the described conduct of the EU when negotiating and acceding to the ECT. Hence, that investors should not be bereaved of their vested rights is a matter of material justice. This holds all the more true where the EU was instrumental in soliciting the investments and changed its position only at a point in time when such investments had been made. 
* Rechtsanwalt and Attorney-at-Law (New York)
Partner, GÖRG Partnerschat von Rechtsanwälten
 ECJ, 6 March 2018, Case C‑284/16, Achmea; ECJ, ECJ, Opinion 1/17 of 30 April 2019, CETA.
 Issue 80 (2/2020), pp. 379 – 427.
 Cf. Foresight v. Spain, SCC Arbitration V 2015/150, Award, 14 November 2018, para. 221, with a list of awards affirming intra-EU arbitration; Reuter, note 2, Part B IV.
 Vattenfall et al. v. Germany, ICSID Case No. ARB/12/12, Decision on the Achmea issue, 17 August 2018, paras. 154/155; Reuter, note 2, Part B
 The reasons for that stance may be institutional rather than legal: Organizations innately tend to attach high priority to their own competences and inter-institutional governance.
 MacLachlan/Shore/Weiniger, International Investment Arbitration, 2007, paras. 1.06, 2.20, 7.01; Reuter, note 2, Part B.
 ECJ, 10 January 2006, C-344/04, IATA and ELFAA, para. 35.
 For more details Reuter, note 2, Part D.
 ECJ, 30 May 2006, Joined Cases C-317/04 and C-318/04, European Parliament v Council, para. 73.
 For more details Reuter, note 2, Part D.
 As for the liability of the EU on the one hand and member states on the other hand in connection with mixed investment agreements in general Armin Steinbach, EU Liability and International Economic Law, Hart Publishing 2017, pp. 133 et seq., pp. 141 et seq.
 For more details Reuter, note 2, Part D; as regards the carve-out ECJ, 13 May 1981, Case 66/80, International Chemical Corporation, paras. 13/14; see also ECJ, 8 April 1976, Case 43/75, Defrenne v Sabena, paras. 71/72.
 ECJ, 29 June 1969, Case 29/68, Milch-, Fett- und Eierkontor GmbH v Hauptzollamt Saarbrücken, para. 3.Wegener in Calliess/Ruffert, EUV/AEUV, 5th ed. 2016, art. 267, para. 49.
 ECJ, 24 May 1977, Case 107/76, Hoffmann-LaRoche/Centrafarm, para. 5; Reuter, note 2, C III.
 ECJ, 5 March 1986, Case 69/85, Wünsche Handelsgesellschaft GmbH & Co. v. Germany, para. 15; For more details Reuter, note 2, Part B III.
 For more details Reuter, note 2, Part B III 3.
 For more details Reuter, note 2, Part D.
 See note 4.
 Reuter, note 2, Part E.