This article explores security cooperation between the Caribbean and Mexico,looking specifically at strategies being pursued to shift the focus in Latin America and the Caribbean from ‘the war on drugs’ to ‘the war on guns’ to address the problem of gun trafficking. This is a shift away from the United States’ priority to that of the region and a move towards a more assertive model of South–South security cooperation. The Caribbean Community and Common Market’s (CARICOM’s) strategy to support Mexico’s tortious and historic lawsuit against American gun manufacturers and to declare a ‘war on guns’ reflects its inability to independently influence the United States’ priorities within the region. Mexico, a Southern country, makes a difference because of its geopolitical relevance to the US, their shared border, and Washington’s attempt to stop the flow of Mexican immigration. We read the Mexico–Caribbean coalition as a significant development in South–South security cooperation (SSSC). Our analysis contributes to an understanding of the nuances and complexities of security cooperation, capacities for scaling up action through SSSC, and the political and legal manoeuvrings involved in challenging hierarchies of power between the so-called global North and South.