In a recent opinion, the European Economic and Social Committee (EESC) has called for the EU to negotiate an ‘inter se’ agreement with the UK and other third states to neutralize the sunset clause of the Energy Charter Treaty (ECT). This would be a crucial step to safeguard the European Green Deal, minimize the ECT’s legacy risks, and prevent investment arbitration from obstructing climate action. The EESC opinion draws on ideas outlined in a IISD model inter se agreement.