Business entities play an important role in contemporary world, especially within the context of globalisation. Private security companies (PSCs) are entities that exchange security services for financial gain; their activity is constantly increasing and is relevant under both the law of peace and war. The present research studies the criminal regulatory network currently in place for PSCs. The analysis focuses on the interconnected liabilities of PSCs as legal entities and their personnel. The regulatory network is inspected from the EU viewpoint, within the framework of international law. The EU regulation is analysed in the light of the common foreign and security policy as well as cooperation in justice and home affairs. At the national level, the regulation of EU member states is compared to the legslation of non-European countries. The international implications of the EU regulation are studied by taking into account customary and treaty law, both inside and outside international humanitarian law. The research aims to: (1) understand what criminal rules apply to PSCs and their personnel; (2) investigate the crimes likely to be committed by PSCs and their personnel, the subjective scope of criminal liability, exceptions to liability, criminal procedures and sanctions; (3) evaluate the coherence and completeness of the regulatory network and show possible reform perspectives. The Project is relevant to the priorities of the FP7 Programme. It is specifically related to the areas ‘Socio-Economic Sciences and Humanities’ and ‘Security’.