What explains the choice of means and methods of warfare by armed groups? Conversely, why would some groups choose not to use certain weapons? Beyond the legitimacy- and reputation-based explanations common in existing literature, this article highlights the role of tactical utility, inherent costs, and normative biases of specific means and methods in shaping these decisions. Through a combination of congruence analysis and comparative methods, the article examines why the United Self-Defense Forces of Colombia (AUC), while employing a wide range of brutal forms of violence, generally avoided using landmines, contrasting this restraint with the behavior of other Colombian armed groups. Although the lack of tactical utility seems to be the primary driver of the non-use of landmines, the costs and stigma associated with using mines influence how the AUC perceived their utility. The findings underscore the importance of context-specific factors in the decision-making processes of non-state armed groups and contribute to broader discussions on the disaggregation of violence in civil wars.