In 2018, the Court of Justice of the European Union (CJEU) declared arbitration clauses in intra-EU bilateral investment treaties (BITs) incompatible with EU law, extending this ruling to multilateral investment protection agreements such as the Energy Charter Treaty (ECT) in 2021. Section 1032 II German Code of Civil Procedure (ZPO), a provision solely known to German law, allows for the invalidation of arbitration agreements even before the stage of enforcement. The Netherlands and Germany sought to apply this provision to intra-EU International Centre for Settlement of Investment Disputes (ICSID) arbitrations, resulting in conflicting decisions by the Higher Regional Court Cologne and the Court of Appeal Berlin. On 27 July 2023, the German Federal Supreme Court affirmed the inadmissibility of the intra-EU investor-state arbitrations at ICSID, aligning with the previous decisions of the Higher Regional Court Cologne and the CJEU. Among other considerations, the German Federal Supreme Court ruled on the applicability of section 1032 II ZPO to ICSID arbitration proceedings, primarily justifying its decision by emphasizing the primacy of EU law. This case note analyses the German Federal Supreme Court’s reasoning and provides insights into the practical implications and the broader impact on intra-EU investment arbitration proceedings.