In 2011, the European Union (EU) concluded the first of a ‘new generation’ of free trade agreements that contained a separate chapter with obligations relating to ‘trade and sustainable development’ (TSD) issues. This was the Free Trade Agreement with the Republic of Korea. The EU formally initiated its first TSD complaint, under this agreement, in 2018. This labour complaint came after a non-paper of the European Commission promised ‘more assertive’ use of the soft dispute mechanism for TSD obligations, following years of pressure by various stakeholders. This non-paper remained apologetic about hard sanctions but promised a review in 2023. This article aims to study to what extent the EU delivered upon its promise to use the soft dispute mechanism more assertively during its first TSD proceedings. It finds that the EU was not prepared to act assertively in relation to certain issues (collective bargaining and the right to strike) and certain workers (in the public and export sectors) during the proceedings before the ad hoc Panel of Experts, which ended in 2021. It argues, in particular, that the EU missed a major opportunity to use its bargaining leverage vis-à-vis Korean consumer conglomerates. https://academic.oup.com/ejil/article/33/2/607/6647756 Aleydis Nissen, ‘Not That Assertive: The EU’s Take on Enforcement of Labour Obligations in Its Free Trade Agreement with South Korea’ (2022) 33(2) European Journal of International Law 607.