The use of private military and security companies (PMSCs) is a growing phenomenon in Latin America and the Caribbean, where complex situations are common. Even though the use of PMSCs is not per se problematic, the lack of an efficient international and national regulatory framework for PMSCs raises several concerns about the protection of human rights. This study aims first to analyze PMSCs’ activities and regulation thereof in conditions in which there is a mix of several types of situation, such as armed conflict and criminal activities or post-disaster and post-conflict. This complexity challenges the identification of the law applicable—international humanitarian law or/and international human rights law— and, thus, challenges the enforcement of any adequate regulation for PMSCs. Three case studies—Colombia, Mexico, and Haiti—illustrate these issues. In Colombia, a noninternational armed conflict has been ongoing for approximately fifty years alongside criminal activities linked to drug trafficking. In Mexico, the War on Drugs has escalated to a situation technically classifiable as an armed conflict. Finally, in Haiti, the situation evolved from an armed conflict (2004-2007), to a situation of peace with a high criminal rate before the earthquake (2007-2010), to a post-earthquake disaster situation in which criminality is rising but the intensity of the violence has not reached the level to be classified an armed conflict (2010-present). In order to implement international standards concerning PMSC regulation it is necessary to consider both bodies of law and force territorial states to assume their responsibilities. Considering these elements I then argue that the Inter-American System of Human Rights can play a significant role in improving PMSCs’ regulation in Latin America and the Caribbean thanks to is avant-gardiste features. Its jurisprudence on non-state actors coupled with its use of external sources to interpret the American Convention on Human Rights would allow the implementation of international norms, including international initiatives on PMSCs, in the region.