On October 2, 2002, the 1998 UK Human Rights Act, which incorporated the European Convention on Human Rights into UK law, entered into force. The Act made a remedy for the breach of the European Convention available in UK law without the need to go to the European Court of Human Rights in Strasbourg. Relatives of individuals who had been killed by UK troops in Iraq brought suit under the European Convention, pursuant to the Act, in UK courts, initially for the deaths of six Iraqi civilians. The prevailing case law on the extraterritorial application of the European Convention at the time was defined in the Bankovic decision and required that the violations had to have taken place within the borders of a contracting state. The deaths of the Iraqi citizens, however, took place in Iraq, which was not part of the UK and not a contracting state.
The British Government, at the domestic level, contested the plaintiffs' assertion that the UK was sufficiently in control of Basra at the time, as an occupying power, to be responsible for the protection of the human rights of all the civilians in Basra. It did, however, concede that it was responsible for the death of one of the six Iraqis, who had died while in custody of UK troops. In my view, this concession opened the door to the European Court's overturning the Bankovic decision and holding the UK responsible for the deaths of all six Iraqi civilians when the case was taken to Strasbourg and decided in 2011.
The ICC conducted a brief preliminary investigation into Iraq/UK, which was closed in 2006. In March 2014, the Prosecutor of the International Criminal Court (ICC) re-opened an investigation into war crimes committed by the UK military in Iraq from 2003-2008, pursuant to an Article 15 communication filed by the European Center for Constitutional and Human Rights and the Public Interest Lawyers. Despite the fact that the ICC concluded that war crimes had been committed by UK armed forces against Iraqi civilians in detention during this period and over 3,000 cases had been brought, in a Report issued on December 9, 2020, the ICC closed the investigation, declaring it inadmissible under Article 17's complementarity requirement. The ICC emphasized that it is not a human rights body "[R]ather it is tasked with determining whether it should exercise its own competence in a criminal case, in place of the primary duty which belongs to a State. To do so, the Court must be satisfied that no relevant proceedings have been undertaken, or if they have, that these proceedings were not genuine, either because the State is unalbe to undertake genuine proceedings, or because the State is unwilling to do so in the sense that it has taken steps to shield perpetrators from criminal justice."
Despite the fact that during the domestic process went on for ten years and not one single case was submitted for prosecution, the ICC Prosecutor did "not conclude that the UK authorities have been unwilling genuinely to carry out relevant investigative inquiries and/or prosecutions or that decisions not to prosecute in specific cases resulted from unwillingness genuinely to prosecute."