At the time of the THERESA project’s inception in 2021, research on green hydrogen was predominantly focused on technical and economic aspects, with limited legal scholarship on the subject. Hydrogen regulation in the EU was governed by a fragmented framework of directives, with no dedicated legal instruments addressing its production, trade, or integration. Since then, the THERESA project has made significant contributions to advancing legal scholarship on hydrogen regulation, filling critical knowledge gaps and offering practical solutions to existing legal challenges. The research has produced groundbreaking insights into hydrogen regulation and governance. It has mapped the legal fragmentation affecting hydrogen infrastructure, highlighted the regulatory barriers to integrating hydrogen into national energy and climate policies, and examined hydrogen certification schemes to facilitate global trade. A new conceptual framework, the Hydrogen Prism, has been developed to analyse regulatory cohesion, risk mitigation, and compliance in the heavy-duty transport sector. The project has also pioneered legal research on citizen participation in hydrogen governance, revealing the limitations of the current “one-size-fits-all” approach and advocating for an equity-based legal framework to ensure a just energy transition. Furthermore, circular economy principles have been applied to hydrogen production and infrastructure, identifying legal barriers that hinder waste valorisation, resource efficiency, and sustainable water use. The project has also explored cross-sectoral regulation, providing a framework for regulatory sandboxes in hydrogen valleys, which could serve as experimental spaces for legal innovation and cross-sectoral integration. These findings have immediate policy relevance, particularly in light of recent regulatory developments. The comparative EU-US analysis conducted within THERESA offers valuable insights for regulatory learning and harmonisation. Moreover, the project has identified that current EU RFNBO requirements may create unintended barriers to international trade, necessitating adjustments to align with the EU’s hydrogen import objectives. By combining doctrinal, empirical, and comparative legal methodologies, the THERESA project is setting a new benchmark in hydrogen regulation research. Its results provide a robust legal foundation to support the EU’s vision for a sustainable, legally coherent, and globally integrated hydrogen economy.
