Fostering the green and digital transitions have become existential policy challenges. But the interdependencies of these challenges urgently requires their ‘twinning’ to succeed. Twin-Law elaborates an experimentalist, synthetic study that fills this gap, by interconnecting the EU ‘Green Deal’ and ‘Digital Age’ legal-regulatory models that are guiding the European twin transition. This will enable judges, policymakers, and researchers to dynamically appraise the powers and responsibilities of key co-regulatory authorities across the green/digital divide and further develop an integral European policy model that can inspire this ‘twin transition’ elsewhere in the world.