This chapter begins by motivating the puzzles the book seeks to answer. Why do Rio de Janeiro’s drug-trafficking gangs govern neighborhoods? Why do some of these gangs rely on violence and coercion while others resolve disputes, offer welfare, and organize cultural activities for residents? This book argues that gangs govern in these ways because they need the obedience and support of local residents to survive amid shifting relations with rival gangs and the police. This chapter outlines a theory of criminalized governance which revolves around the relations that emerge between gang members and residents within distinct security environments. This theoretical framework builds on three traditions that view criminalized governance akin to processes of state formation, rebel governance, or state perversion. Finally, this chapter outlines its mixed method approach, and describes the methodological and ethical considerations involved in eighteen months of participant observation in three rival gang territories, 206 semi-structured interviews with residents and gang members, and the collection of more than 400 archival documents and a dataset of more than 20,000 anonymous denunciations.