Critical terrorism studies (CTS) rightly placed the theme of expertise within the core of its original project, critically illuminating the role of terrorism ‘experts’ in shaping the knowledges, discourses, practices, and the politics of terrorism and counterterrorism. Acknowledging the substantial evolutions within the marketplace of terrorism expertise over the last decade, this chapter makes the case that CTS must reengage with the theme of expertise moving forward. In addition to the substantially evolved landscape since the first decade post-9/11, this chapter argues existing frameworks utilised by CTS, such as epistemic communities, are insufficient to fully explore the dynamics of expertise. Moving forward, this chapter calls for greater utilisation of the sociology of expertise literature as one possible avenue for reengagement. As one exploration down this avenue, this chapter will introduce the way in which Twitter has become a highly consequential space for the struggles to shape the character of expertise on the Islamic State group.