فردین رستمی امانی

International relations has been witnessing of many Non –governmental players in the arena under the name of the Private Military and Security Companies (PMCs) in the recent decades. Their ever increasing growth and participation in Internal and international armed conflict have caused many problems. One of the most important of these problems is the determination of responsibility for unlawful activities of the PMSCs and ascertaining of the responsible state in this regards. The States have been divided into three groups; the state who employ the PMSCs, the state whom the PMSCs are national of it and the state which they play role in its territory. Now the problem is which state shall be responsible for unlawful activities of the PMSCs. This essay is going to ascertain due responsible for such acts based on valid International documents and regulations. Fortunately, there are two main internationally recognized documents; the Draft Articles on the Responsibility of States for Internationally Wrongful Acts ("Draft Articles") by the International Law Commission (ILC) in August 2001 and the Montreux Document which has been used by the author.