We advance understandings of defensive institutional work by examining how ‘national interest’ rhetoric is used to defend national institutions in response to organizations’ institutional change efforts. To tackle this question, we analyze policy argumentation on 13 institutional change initiatives devised by trade, political, or civil society organizations that have sought to introduce national legislative change in Switzerland between the late 1980s and early 2020s. Our analysis identifies three novel types of defensive institutional work––protection of chosen institutions, reaffirmation of shared institutions, and sustenance of controlled institutions––by which policymaking responds to organizations’ change initiatives and portrays their rejection (or acceptance) as being of national interest. Our study contributes to the literature by expanding our knowledge of defensive institutional work on national institutions that have been subjected to ‘insider-driven’ change efforts. We also add a missing piece to the organizational literature on rhetoric by presenting and dissecting ‘national interest’ as a powerful rhetorical device mobilized to shape organizations’ institutional environment.