Things have changed. There is no longer an adequate fit between international law and the threats that we face. In a globalised world, we can be struck at at any time, by any one. International law needs to adapt so as to allow us to take action on the basis of the view that shifty-looking people are, generally, shifty and no doubt up to something, just like we adapted domestic law to do the same. After all, bad people do bad things, and when we're fighting them, it can sometimes be necessary to adopt tactics which bear certain operational similarities to those that they use. Because they are criminal, we may need to be criminal to fight them. Some might think that by adopting such tactics, we become like them. I disagree. I think our willingness to compromise the very values we are fighting to protect demonstrates precisely how committed to them we are.
Some may further say that international law codifies principles of restraint and purposefully sets the bar of justification high so as to avoid the death, destruction and suffering that inevitably arrive with any declaration of war. This may have been true in the past, when, in fact, one dead civilian was equal to ten of today's dead civilians, but the world has changed, and so the moral principles which used to underlie international law are now archiac and outdated. Our world has become globalised, and so innocent people's lives are now worth less. In line with this step-change, we feel that international law ought to allow us to discount the burdens of morality appropriately. I have three changes in particular in mind: I want to be able to boil people alive; I want to be able to bomb places because I feel like it; and, as a figleaf, I want to be able to send in troops to rescue the starving millions.
Update, 6/4/06: Jim Bliss has a longer piece making much the same points, which also has some links to some other comments on Dr Reid's pronouncements, and Jarndyce points out that having broken international law, the British government is hardly in the best position for proposing alterations to it.