Drug-related violence in Mexico has claimed over 34,000 lives since Mexican President Felipe Calderón initiated his crackdown on Mexico’s drug cartels in 2006 with the deployment of military troops to Michoacán. Somewhat surprisingly, Mexico’s drug war has garnered rather little attention from the international community, despite a wealth of headlines in popular media. This Note takes up the question of international criminal enforcement in Mexico against Los Zetas, widely considered Mexico’s most violent drug cartel. By setting up a hypothetical—but possible—International Criminal Court (ICC) prosecution of Los Zetas cartel leader Heriberto Lazcano, this Note demonstrates that the ICC Prosecutor could likely show sufficient evidence of Lazcano’s liability for Crimes Against Humanity for the purposes of obtaining an arrest warrant from the Pre-Trial Chamber. However, assuming Mexico would in fact prosecute Lazcano domestically, significant admissibility issues would arise given that Mexico lacks a domestic codification of Crimes Against Humanity, the relevant ICC crime. This presents a unique situation to analyze whether a concurrent domestic prosecution for “ordinary crimes” could lead to a finding of “unable to prosecute” under Article 17 of the Rome Statute, which would result in the admissibility of the case before the ICC despite concurrent state action. The ordinary crimes analysis with respect to Mexico’s inability (or ability) to prosecute this potential case has broad implications for the nature of the ICC’s complementarity regime as an effective guardian of state sovereignty.