Private military and security companies (PMSCs) personnel must always be held accountable for violations committed under international human rights and humanitarian law, the United Nations Working Group on the use of mercenaries said today, reiterating its call for global regulation of private security. The expert body’s appeal comes seven years after the killing of 17 Iraqi civilians, including children, by Blackwater personnel in Baghdad’s Nissour Square. On 22 October, four private military contractors involved in the killings were prosecuted and convicted of manslaughter and murder by a US federal jury. “We welcome the fact that prosecutions were finally brought, putting an end to the cycle of impunity that prevailed since 2007 and aggravated the suffering of victims and their families,” said Patricia Arias, who currently heads the five-strong group of independent human rights experts.“However, such examples of accountability are the exception rather than the rule,” she stressed. “The difficulty in bringing a prosecution in this case shows the need for an international treaty to address the increasingly significant role that private military companies play in transnational conflicts.”