Procedural Posture and Purpose

This document constitutes the Concurring and Dissenting Opinion of Arbitrator Antolín Fernández Antuña in the ICSID proceedings between Mainstream Renewable Power Ltd and the Federal Republic of Germany. While Arbitrator Fernández Antuña concurs with the majority's dismissal of the claims on the merits, he respectfully dissents on the tribunal's finding of jurisdiction, concluding that the Energy Charter Treaty (ECT) does not contain a valid offer to arbitrate intra-EU disputes.

Jurisdiction Ratione Voluntatis

The dissent advances a systemic interpretation of Article 26 of the ECT, applying the customary rules of treaty interpretation codified in Article 31 of the Vienna Convention on the Law of Treaties (VCLT). Arbitrator Fernández Antuña reasons that the phrase "of another Contracting Party" in Article 26(1) ECT cannot be read in isolation. Instead, it must be construed in light of the ECT's definitional provisions—specifically Article 1(3), which explicitly recognizes Regional Economic Integration Organizations (REIOs) and the binding nature of their internal legal orders. Integrating EU law as a relevant rule of international law applicable between the parties pursuant to Article 31(3)(c) VCLT, the dissent concludes that the ECT precludes intra-EU investor-State arbitration. To hold otherwise would generate an irreconcilable conflict with the autonomy and primacy of the EU legal order, as affirmed by the Court of Justice of the European Union in Achmea and Komstroy.

Merits: Fair and Equitable Treatment and Expropriation

Concurring with the majority on the merits, Arbitrator Fernández Antuña provides supplementary reasoning regarding the Fair and Equitable Treatment (FET) and expropriation standards. He emphasizes that the German Offshore Wind Energy Act of 2017 (WindSeeG) constituted a legitimate, bona fide exercise of the State's police powers aimed at environmental and climate protection. The opinion underscores that international investment law does not impose strict liability for regulatory changes; rather, state liability must be predicated on fault. Because the regulatory framework was amended proportionately and without fault to serve a compelling public interest, the measures did not breach the FET standard. Consequently, the absence of an FET breach a fortiori precludes any finding of indirect expropriation, notwithstanding any alleged diminution in the value of the claimants' shares.