This paper examines the discourse of ‘shared responsibility’ that the governments of the United States and Mexico created through the 2008 Mérida Initiative. This discourse fixed the terms of an unruly debate that stood in the way of bilateral cooperation – are Mexico's drug cartels terrorists, and if so is Mexico in danger of failing? Specifically, the discourse does three things. First, it clarifies the formal position of both governments that Mexico's drug cartels are criminals, not insurgents. Second, by using the term ‘transnational criminal organisation’ (TCO) to label the cartels, the United State accepts some responsibility for them. Finally, the discourse establishes a territorial notion of sharing so that US participation inside Mexico is limited. Although ‘shared responsibility’ has been characterised as a ‘paradigm shift’ in how the two countries deal with one another (Benítez Manaut 2009, Revista Mexicana de Política Exterior 87), I argue here that it reinforces a militarised status quo. By defining ‘shared responsibility’ as an obligation between states, the two countries do not have to articulate a joint responsibility to Mexico's civilians, who bear the brunt of both the cartels and the bilateral fight against them. This framing also helps explain the US government's muted response to abuses by the Mexican military since the agreement took effect.