This past summer, British Prime Minister Gordon Brown announced the establishment of an inquiry into the UK’s involvement in the Iraq War. The Iraq Inquiry, which is independent of the government, began work at the end of July. The committee will consider events from the summer of 2001 until the end of July 2009 when all British forces left Iraq. This means that the inquiry has a mandate to consider the lead up to the Iraq war, including the circumstances in which the decision was taken to commit the UK to the invasion, as well as the period of the conflict and the post conflict reconstruction. In establishing the inquiry, the Prime Minister stated that the
“the primary objective of the committee will be to identify lessons learned. The committee will not set out to apportion blame or consider issues of civil or criminal liability.” (see here at column 24, 2nd para)
The Inquiry will be conducted by a team of five headed by a former civil servant, Sir John Chilcot. It includes an academic (Sir Lawrence Freedman), a historian (Sir Martin Gilbert), a former diplomat (Sir Roderic Lyne) and a member of the House of Lords (Baroness Usha Prashar).
International lawyers, and indeed the general public would be interested to know, that the Chair of the Inquiry announced in its initial press conference that the inquiry would seek to
form impartial and evidence-based judgements on all aspects of the issues, including the arguments about the legality of the conflict. (see here)
Given that it is unlikely that the question of the legality of the war in Iraq will come before an international tribunal, the Iraq Inquiry may well be the most important public and formal process for the determination of the legality of the UK’s (and US’) use of force in Iraq. Last week, the Inquiry announced the appointment of Dame Rosalyn Higgins as its international law adviser. Dame Rosalyn was Professor of International Law at the London School of Economics up until 1995 when she became a Judge of the International Court of Justice (ICJ). She was President of the ICJ from 2006 until February 2009 when she stepped down from the Court. In addition the Inquiry has engaged General Sir Roger Wheeler, the former Chief of the General Staff (i.e head of the British Army) as its military adviser.
Like the Prime Minister, Chair of the Inquiry has stressed that “the Inquiry is not a court of law and nobody is on trial” (statement at the Chair’s initial press conference). However, there remains some interest as to whether the inquiry could lead to prosecutions, if it were to find that the UK went into the war illegally. The Inquiry has announced that it will call as witnesses the Prime Minister and former Prime Minister Tony Blair. Could Tony Blair be prosecuted for taking the UK into an illegal war? The inquiry will report to Parliament in the summer of 2010 around the same time as the Review Conference for the Rome Statute of the International Criminal Court will take place. The main agenda item (see here) at the Conference are proposals to amend the ICC Statute to include a definition of the crime of aggression and to allow the Court to prosecute those who commit the crime (see proposals here).
Although the UK is a party to the ICC Statute and even if the ICC parties were to agree next summer on a definition of aggression and conditions for the exercise of ICC jurisdiction over that crime, Tony Blair and other UK leaders cannot be prosecuted for aggression by the ICC. This is because the jurisdiction of the ICC over aggression will not be retrospective.
Similarly, the former Prime Minister and others cannot be prosecuted in the UK’s domestic courts for aggression. The crime of aggression is not included as a domestic crime in the UK’s International Criminal Court Act 2001. The House of Lords in R v. Jones  UKHL 16 has recognised that the crime of aggression is a crime under customary international law and that a
“that a crime recognised as such in customary international law (such as the crime of aggression) may, but need not, become part of the domestic law of England and Wales without the need for any domestic statute or judicial decision.” (Lord Bingham, para. 27)
However, in the Jones case, the House of Lords ultimately held that the crime of aggression was not a part of the domestic law of England and could not be incorporated into English without an Act of Parliament. This is on the basis that at least since the 1970s there is a constitutional principle that it up to Parliament to create new crimes. Furthermore, prosecution of individuals for aggression would require determination by the courts of the responsibility of the State engaged in the aggression and this, according to Lord Bingham, would be contrary to
“well established rules that the courts will be very slow to review the exercise of prerogative powers in relation to the conduct of foreign affairs and the deployment of the armed services, and very slow to adjudicate upon rights arising out of transactions entered into between sovereign states on the plane of international law.” (para. 30)