In the modern globalized world, so-called private military and security companies (PMSCs) are employed by a variety of actors in times of both war and peace. They are employed by, and perform a plethora of services for, not only international organizations, NGOs and multinationals, but also States. Given that there are still regulatory gaps in the national and international legal frameworks applicable to PMSCs and that the lines of responsibility often are unclear, State responsibility becomes an important instrument for attaining justice and ensuring respect for international law by private contractors.