Terrorist groups and armed insurgents regularly exploit illicit markets to launder money, traffic illegal goods, and purchase arms. In such an environment, the line between armed political organizations and criminal groups appears to break down. However, through a comparative study of paramilitary groups and Fuerzas Armadas Revolucionarias de Colombia (Revolutionary Armed Forces of Colombia—FARC) in Colombia, this article finds that group goals, the political environment, and membership strongly influence the types of criminal activities a given armed groups undertakes. Thus, the membership and political agenda of sub-state armed groups not only distinguishes them from criminal groups—organized for and motivated by economic gain—but also shapes their criminal behavior.