On 26 January well known writer for The Guardian George Monbiot launched a website www.arrestblair.org, the purpose of which is to raise money as a reward for people attempting a peaceful citizen’s arrest of the former UK Prime Minister for the crime of aggression for his involvement in planning and launching the invasion of Iraq.
The matter turns on the legality of the invasion. As Monbiot puts it:
Without legal justification, the war with Iraq was an act of mass murder: those who died were unlawfully killed by the people who commissioned it. Crimes of aggression (also known as crimes against peace) are defined by the Nuremberg principles as "planning, preparation, initiation or waging of a war of aggression or a war in violation of international treaties". They have been recognised in international law since 1945. The Rome statute, which established the international criminal court (ICC) and which was ratified by Blair's government in 2001, provides for the court to "exercise jurisdiction over the crime of aggression", once it has decided how the crime should be defined and prosecuted.