I think that we are getting into a slightly arcane legal point. Obviously I accept that if it were laid down in legislation what votes should be taken, how they should be taken and in what circumstances, that would open up the possibility of legal challenges—in a way that might not arise if we had a convention. But I was not using the term "legitimising" in its strictly legal sense; I was thinking about the Government's seeking justification for the action that they intended to take.
If we start to look at the detail, we can see that the argument between having legislation and relying on convention is quite difficult. My gut feeling and preference would be for legislation, having introduced a private Member's Bill on the subject a few years ago, but I recognise from that experience the difficulties of drafting and of getting the legislation exactly right. Safeguards are necessary to allow for urgent action and for troops to be able to defend themselves without any fear that that action will create difficulties for them. How do we distinguish between military action and peacekeeping? Is there really a distinction in some cases?
I recall the debate on the Bill introduced by my right hon. Friend the Member for Birmingham, Ladywood and that some of the difficulties that were suggested at that time were somewhat exaggerated. The most important difficulty is one that the right hon. and learned Member for Rushcliffe spoke about in his contribution: the timing of the vote. If Parliament is asked to vote when troops have already been deployed—as it was in the final vote on Iraq—certainly for some people it becomes much more difficult to oppose the war.