Contributor(s): Dr Chaloka Beyani | When does a soldier become a mercenary? When does a private security company become a mercenary army? Although mercenaries are prohibited by international law, many state actors continue to rely on the availability of "guns for hire" as a means of pursuing their international interests without the entrenchment that official military involvement involves. In this short film, Dr Chaloka Beyani talks about how shrinking military ranks has led to the rise of private security companies, and where these de facto "mercenary armies" fit within international law. Dr Beyani is Senior Lecturer in International Law in the Law Department, a member of the Centre for the Study of Human Rights and Chair of its Advisory Board, and a member of the Centre for Climate Change at LSE. He is also the United Nations Special Rapporteur on the Human Rights of Internally Displaced Persons. He joined the Department of Law at LSE in 1996 and lectures in international law and human rights. He was formerly a Research Fellow at Wolfson college, Oxford, with Lectureships in Law at Exeter and St. Catherine's colleges, Oxford, and a Crown Prince of Jordan Fellow, Queen Elizabeth House, as part of the Refugee Studies Centre, Oxford.