Drug gangs and organized criminal groups rarely evolve into structured authorities governing their resident communities. Where this occurs, however, they may effectively replace the state in its most basic functions, and consequently exclude subject populations from the rights and protections supposedly guaranteed by the state. Employing qualitative research methods, this study compares criminal development and state public security policies in Rio de Janeiro and Recife, Brazil. The research is primarily concerned with the development of criminal authority structures, and asks when, where, why, and how they develop. Arguing that the extant literature on organized crime fails to adequately explain this phenomenon—particularly in the case of drug trafficking gangs—I draw from the civil wars literature to theoretically explain the rise of non-state authority structures. The parallels are compelling. In Rio de Janeiro, concentrated illicit wealth created by the cocaine boom in the 1980s attracted an international arms market that helped drug gangs dominate larger territories (i.e. opportunities), while indiscriminate and lethally violent state repression pushed non-criminal publics into a de facto alliance with drug traffickers (i.e. grievance). In this context gangs--and later, militias--developed clear and structured governing functions. Other factors, such as inhibiting geography, also contributed to this authoritative duality. In Recife, by contrast, drug gangs have remained small, disorganized, and unengaged in local political structures. A smaller drug market, flat and vehicle-accessible slums, and a comparatively much less violent police force help to explain the failure of gangs and other criminal groups to develop broader authoritative functions.