Achmea

Achmea refers to the 2018 Court of Justice of the European Union (CJEU) ruling in Slovak Republic v Achmea BV (Case C-284/16), which held that investor-state arbitration clauses in bilateral investment treaties (BITs) between EU member states are incompatible with EU law. The ruling fundamentally disrupted intra-EU investment arbitration by establishing that member state courts cannot refer investment disputes to arbitral tribunals established outside the EU judicial system. Achmea is the doctrinal predecessor to Komstroy (2021), which extended the same reasoning to the Energy Charter Treaty.

The case arose from a BIT between the Netherlands and Czechoslovakia. Achmea BV, a Dutch health insurer, had brought an arbitration claim against Slovakia under the treaty after Slovakia reversed its health insurance liberalisation policy. The CJEU's Grand Chamber ruled against Slovakia on the merits but, crucially, held that the arbitration mechanism itself was incompatible with the EU Treaties because it excluded disputes from the EU judicial framework.

For European energy markets, Achmea is significant as the legal foundation for the Commission's campaign to terminate intra-EU investment arbitration across the energy sector. It directly underpins the Komstroy ruling and the ECT Article 26 infringement proceedings against Hungary over MOL, making it the doctrinal root of the April 2026 infringement package.