The legal community is deeply divided on the question of the legality of using force against Iraq in the absence of a further UN resolution. There are two camps. The first takes the view that military action can be justified without a further resolution either on the basis of self-defence or on the basis that previous UN resolutions, including resolution 1441, authorise the use of force. The second takes the opposite view that, as things stand, there is no actual or imminent threat from Iraq that would justify a "self-defence" response by the UK and that nothing in resolution 1441, or any other UN resolution, authorises the use of force without a further resolution giving clear authority to do so.
The government has been advised on the issue by Lord Goldsmith, the attorney general. His advice is to be disclosed today. All the prime minister has been prepared to say so far is that the UK will not take any action that does not have a "proper legal basis", as he made clear in his answers in parliament last week.
Time is now running out. In the very near future British troops are likely to be committed to battle. They, their families and the public have a right to know what the "proper legal basis" for their action is. Engaging in armed conflict in breach of international law is a precarious business. The idea that the prime minister would end up before the international criminal court for participating in a US-led attack is far-fetched. But military commanders on the ground will not thank the government if any action they take is later judged to have been in breach of international law.
The limits of the potential arguments available to the government are clear. According to the UN charter, there are only two possible situations in which one country can take military action against another. The first is in individual or collective self-defence - a right under customary international law which is expressly preserved by Article 51 of the UN charter. The second is where, under Article 42 of the charter, the security council decides that force is necessary "to maintain or restore international peace and security" where its decisions have not been complied with. In other words, where a UN resolution clearly authorises military action.
The question whether the Article 51 self-defence route justifies a pre-emptive attack has been keenly debated. Article 51 itself is silent on the matter. But even if it does justify a pre-emptive strike, which is surely the sounder position in a nuclear world, any threat to the UK or its allies would have to be imminent and any force used in response to that threat would have to be proportionate before Article 51 can be relied on. The mere fact that Iraq has a capacity to attack at some unspecified time in the future is not enough.