The principle of solidarity and hydrogen markets in the European Union.

This article examines the legally binding principle of energy solidarity in the European Union (EU), as clarified by the Court of Justice of the European Union (CJEU) in the OPAL-Judgment, and its implications for the emerging hydrogen market within the integrated EU energy system. The principle, rooted in Article 194 of the Treaty on the Functioning of the European Union (TFEU), requires EU institutions and Member States to consider and balance the interests of other Member States and the EU as a whole when making energy-related decisions, including those on hydrogen network planning and imports. While hydrogen is promoted as a key element for decarbonization and energy security, current EU draft legislation on hydrogen markets largely defers the complex solidarity assessment to national authorities without clear criteria, potentially causing delays in infrastructure development. The article highlights the need for secondary EU legislation to specify assessment criteria and priorities under the solidarity principle to provide legal certainty and facilitate the swift development of a European hydrogen market aligned with broader EU climate and energy goals.