US: The US-led invasion of Iraq was illegal and has weakened the power of international law to prevent war, according to former attorney general and president of the High Court, Declan Costello.
In a lengthy article in the current Irish Law Times, Mr Justice Costello examines the reasons advanced by the administration of the United States and the British government for going to war in Iraq, and concludes that they contravene international law.
Two reasons were advanced by the US government for the invasion, he said: self-defence and the implementation of UN resolutions; while only one was advanced by the UK government, that the invasion was justified by existing UN resolutions.
The self-defence justification was combined with a new theory of pre-emptive force on the basis of past actions by Iraq. Mr Justice Costello points out that this had been rejected by the secretary general of the UN as "a fundamental challenge to the principles on which, however imperfectly, world peace and stability have rested for the last 58 years".
He added: "It is highly improbable that an international court would regard that the use of force against Iraq was an exercise of the right of self-defence permitted by international law."
Turning to the question of the justification provided by UN resolutions, he points out that the early 1990 resolutions cited by the UK government related to the withdrawal of Iraqi forces from Kuwait.
Once this had been achieved, these resolutions were no longer relevant.
The question of continuing the 1990 invasion of Iraq to achieve the overthrow of Saddam Hussein was considered, but rejected on the basis that it was illegal under international law, Mr Justice Costello writes.
He quotes the autobiography of the then British prime minister, John Major, who wrote in 1995: "There was no resolution empowering the allies to go into Baghdad and drag Hussein out by the heels."
Referring to Resolution 1441, passed in November 2002, Mr Justice Costello said that it makes clear the earlier resolutions could not be revived, and that the UN Security Council would have to reconvene and consider the situation if Iraq did not comply with the resolution.
Stating that many issues of great importance were raised by the invasion, he said: "In the future other countries may try to use them to justify the use of force in international disputes."
There should now be widespread discussion in the international legal community as to how these legal effects of the invasion could be minimised, he said.