Small hydropower plants (SHPs) are posing a significant risk to the environment in Europe, whilst their contribution to the energy sector is rather low. This article is examining civil society organisations (CSOs) lobbying activity, during 2017-2018, on opposing the construction of SHPs in Ukraine and Moldova. It is argued that CSOs framed their cause as a legal issue, and not just as an environmental one, aiming at amplifying their persuasive power. First, it is analysed how CSOs framed their cause when interacting with citizens and media, and second, with international organisations. Framing is systematically studied based on media content analysis in both countries and on reports published by CSOs within the Eastern Partnership framework. The findings contribute to a better understanding of framing, by bridging the literature on social movement and transnational climate governance.