16.1 The Achmea ruling has unleashed a storm in the European Union designed to shatter the foundations of investment arbitration under bilateral investment treaties in force between Member States (intra-EU BITs). In just two years, 23 Member States agreed to terminate all intra-EU BITs concluded between them and to remove investment arbitration based on those treaties from the range of legal remedies available to investors who are nationals of a signatory Member State against State measures taken by another signatory Member State where they had invested. We will therefore examine two main aspects of the relationship between EU law and investment arbitration, namely the challenge to the jurisdiction of arbitration tribunals by the Achmea ruling and the disappearance of the intra-EU BITs under the Multilateral Agreement, the ‘Achmea’ Agreement.