Mexican President Felipe Calderón has relied heavily on the armed forces to fight drug-related violence and organized crime. The need to improve public security is clear. Mexico is facing violent turf battles among powerful drug cartels, an influx of sophisticated weapons, and a large number of kidnappings and executions in several states. While engaging in law enforcement activities, Mexico's armed forces have committed serious human rights violations, including enforced disappearances, killings, torture, rapes, and arbitrary detentions. Such horrific crimes destroy public trust, undermining rather than furthering efforts to curb drug-related violence and improve public security. An important reason such abuses continue is that, in practice, Mexico allows military officers involved in law enforcement activities to commit human rights violations with impunity. It tolerates the military investigating itself through a system that lacks basic safeguards to ensure independence and impartiality. This report describes 17 cases involving egregious crimes by soldiers against more than 70 victims, including several cases from 2007 and 2008. None of the military investigations of army abuses analyzed here has led to a criminal conviction of even a single soldier for human rights violations. A civilian investigation was conducted in one of the cases and led to the conviction of four soldiers. The military invokes the Code of Military Justice and a strained constitutional interpretation to justify exerting jurisdiction over the cases. Civilian prosecutors have typically accepted the military's jurisdiction grab. But this outcome is not prescribed by Mexico's Constitution and is inconsistent with a recent binding Supreme Court decision. And international law is clear that serious human rights abuses must be subject to effective, independent investigation and prosecution, standards that the Mexican military justice system manifestly does not meet. The Calderón administration should ensure that serious military abuses against civilians are prosecuted by civilian officials in civilian courts.