This chapter examines the Mexican War on Drugs under President Felipe Calderón’s administration (2007–2012), focusing on the strategic use of protected areas by criminal groups during this period and the resulting challenges for environmental and public security agencies. This chapter explores how the Mexican War on Drugs modified the dynamics of environmental conservation within protected areas, including the development of personal protection strategies for the personnel of the National Commission of Natural Protected Areas (CONANP), researchers and students, and rural and indigenous communities, as well as the development of public policies aimed at strengthening security within these territories. Methodologically, documentary analysis and interviews with directors and environmental inspectors of protected areas at the national level are used to provide an overview of the conditions of public security and environmental conservation during the Mexican War on Drugs and the Post-War Period from the perspective of protected areas and to serve as a frame of reference and documentation of the fight against drug trafficking in areas that did not occupy the spotlight of public and political interest in Mexico during this period of time.