Concerns have been raised about the legality of the United States and the United Kingdom launching a war against Iraq.
Liberal Democrat legal affairs spokesman Lord Goodhart and Labour MP Ross Cranston, the last solicitor general, argued opposing cases on BBC Radio 4's Today programme.
Lord Goodhart believes a second UN resolution is necessary.
The argument seems to have come down entirely to the interpretation of the existing
resolutions on the Iraq situation, particularly 1441 which was passed by the security council in November.
I do not believe that that authorised armed intervention without a second resolution - and that seems to have been the attitude of our government at one time.
Sir Jeremy Greenstock, our ambassador at the United Nations, said on 8 November that there is no automaticity in the resolution.
Resolution 687 which was passed at the end of the Gulf War in 1991 specifically authorised the use of sanctions, and that is continuing up until this day.
I certainly don't believe that authorises armed intervention without a further resolution.
Frankly the government's case depends almost entirely on what is a questionable interpretation of some very ambiguous words in the resolution 1441 - "serious consequences".
We have to recognise that there is a system of international and that does have to be observed if we want an international system that is based on the rule of law.
Kosovo is now used as a basis for a different argument - the right of humanitarian intervention.
That is now accepted by many international lawyers but that is not the basis on which we are claiming to go into Iraq.
I think that a second resolution is necessary.
We are now in a situation where we need to be sure that we have legal justification for what we are doing.
The government has made it clear all along that they are going to act in accordance with what they understand to be the law and I think their understanding is wrong and most international lawyers also feel that it is wrong.
Ross Cranston believes the UK and the US have legal backing
First of all there is 1441 itself and that refers back to these other resolutions.
Resolution 687 in particular required Iraq's disarmament and the ceasefire in 1991 was based on that disarmament, which hasn't occurred.
But there is also another aspect to it in that when we went into Kosovo we didn't have express authorisation from the security council.
Russia and China said they would veto any resolution. So even though we didn't have express authorisation, even though it didn't fall within the self defence provision in the charter, nonetheless there was a justification.
I agree with Lord Goodhart that the rule of law internationally is absolutely crucial.
I think you can draw from that sort of case that international law has to move with the times.
You can't simply be frozen back in 1945 in terms of what the UN charter said.
If there were to be an express resolution there would be no doubt about it.
It would be cleaner if you had a further resolution.
As in Kosovo, as in a whole range of other cases that have happened over the last decades, there hasn't been express authorisation.
In Kosovo, what happened afterwards was important in giving legitimacy to what happened with the Nato action.
Similarly in this case, if there were to be a UN-supervised reconstruction of Iraq that would
help in the legitimacy.
I agree with Lord Goodhart that the rule of law internationally is absolutely crucial. In most cases these are not matters that are going to go before the world court.
So one advances respectable arguments that say the action is legitimate.
I'm quite satisfied that it is without a second resolution.