This paper focuses on the European Chemicals Agency (ECHA) and on the way knowledge- production and the production of governance norms are articulated through and around it in the context of the Europeanization process. The ECHA, established by the 1907/2006 Regulation concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH), is major space of changing regulatory knowledge. As such, it has to be examined within its complex network of co-produced practices, culture, norms and procedures, which respond over time to a variety of industrial, scientific or political challenges. Majone (2000) suggests that the delegation of powers to independent regulatory agencies, embedded in transnational networks, should allow achieving all claims of subsidiarity, accountability and efficiency. Elaborating on Jasanoff and Carpenter, the main argument of this paper is that in order to achieve legitimacy, the regulatory agency operates under a set of institutional, cultural and political considerations that invites various publics to contribute to the underlying dynamic of cryptofederalism. I will follow the regulatory careers of two chemical substances and focus on the issue of legitimacy making in the articulation of the national and European agendas with the pressure of industrial interests.