The British Defence Secretary John Reid has called for changes in the rules of war in the face of "a deliberate regression towards barbaric terrorism by our opponents."
He has put forward three areas for re-examination:
The treatment of international terrorists
The definition of an "imminent threat" to make it easier to take pre-emptive action
When to intervene to stop a humanitarian crisis.
Perhaps the most controversial element was the first.If we do not [re-examine these conventions], we risk continuing to fight a 21st Century conflict with 20th Century rules, John Reid, Defence Secretary.Although he framed his speech in the form of raising questions rather than proposing answers, he came close to suggesting that the way to end the "anomaly" of the US prison camp at Guantanamo Bay was to change international law.
"Anomaly" is the word chosen by the British Prime Minister Tony Blair to describe Guantanamo and it has never really been defined. Mr Reid went some way towards doing that.
There are two ways of ending an anomaly - remove the anomaly or change the situation that makes it one. He appeared to favour the latter.
"On the one hand it is against our values," he said during questions after a speech to the Royal United Services Institute (RUSI) in London.
"But we need to understand how we got to this unsatisfactory anomaly. It is not enough to say that it is wrong. We ought to discuss how it happened."
How it happened, he suggested in his speech, was 11 September 2001 "proved beyond doubt that, while no one can be sure that the era of war between great powers is entirely over, we certainly now face a new enemy.
Guantanamo Bay: how to end the 'anomaly'?
"We now face non-state actors capable of operating on a global scale, crossing international borders, exploiting the teachings of a great, peaceful religion as justification for their murderous intent."
The Geneva Conventions, he said, were created more than half a century ago, when the world was almost unrecognisable to today's citizens.
"Those conventions dealt with important aspects of the conduct of war - how the sick and injured, and prisoners of war are treated; and the obligations on states during their military occupation of another state.
"I believe we need now to consider whether we - the international community in its widest sense - need to re-examine these conventions. If we do not, we risk continuing to fight a 21st Century conflict with 20th Century rules."
The implication of what he was saying that there should be a new category of international prisoner to cover al-Qaeda-type terrorists who are a new kind of fighter. They are not affiliated to any state and therefore do not strictly come within the Geneva Conventions, which refer to soldiers or militias in uniform.
The United States uses the term "unlawful combatants" for its Guantanamo Bay prisoners, but this is not a term used in the Third Convention covering prisoners of war. There is a list of all those who do qualify, but "terrorist" is not one of them.
The legal position of the prisoners is one that has been in constant dispute. In 2004, the US Supreme Court overturned lower courts and ruled that prisoners did have the right to petition US courts. A UN team argued in February that the United States had failed to follow international law.
Mr Reid said the question was "to what extent we could impose on non-state actors the same constraints we apply to ourselves. We need to make people feel the consequences of their actions."
His speech frustrated some listeners there who wanted answers not just questions.After the disaster of Iraq, the idea that the doctrine of the pre-emptive strike should be expanded will be met with incredulity in the West, Nick Harvey, Liberal Democrat spokesman.But he got support from Sir Paul Lever, the RUSI chairman, who was at the heart of the diplomatic establishment during his time at the Foreign Office as an ambassador and chairman of the Joint Intelligence Committee.
"The existing international law might not be adequate," he said. "The standards have to reflect the reality of the deployment. These are no longer straightforward."
However, Elizabeth Wilmshurst, the former Foreign Office legal adviser who resigned over the invasion of Iraq and who is now a senior fellow on international law at the Chatham House think-tank in London, opposed the idea of changing the Geneva Conventions on prisoners.
"Although the law might be made more explicit," she told the BBC News website, "the problem is not so much the rules as the enforcement.
"Human rights and humanitarian law applies to these prisoners and ought to be complied with. In any case, it is very difficult to see the world agreeing on changes in the present context."
Mr Reid's two other suggestions concerned the definition of the imminence of a threat which would justify pre-emptive action and the circumstances in which an intervention on humanitarian grounds could take place.
International law already allows self defence against an imminent threat, but how imminent it has to be remains for debate. President Bush has taken that a stage further with his doctrine of pre-emption and it seems that Dr Reid wants to go down that same path.
The war in Afghanistan had been justified on clear legal grounds, he said, but other situations might not be so clear.
"Difficult as it is, I think all of us here - including representatives from academia, the legal profession, diplomacy and journalism need to consider these issues now rather than waiting for the next threat to come along."
Humanitarian intervention has already been looked at by the UN, which has agreed the theory of the "responsibility to protect."
Mr Reid welcomed that move but suggested that it was not enough.
"The question that people standing in a bus queue in my constituency ask when they see on their TV what is happening in Darfur, Rwanda, Congo or elsewhere is not: 'Why are we interested in intervening?'
"The question they ask is: 'Why aren't we doing more to help these people?'"
The British Liberal Democrat defence spokesman Nick Harvey reflected the concern felt by those who opposed the Iraq war that Mr Reid was trying to clear the way for future actions.
"After the disaster of Iraq, the idea that the doctrine of the pre-emptive strike should be expanded will be met with incredulity in the West and with alarm in the ministries of Tehran," he said.
"If Mr Reid is inviting us to endorse American practices such as indefinite detention, or international rendition, they must be emphatically rejected," he said.
"Compromising on established values and principles would not only be wrong, but would undermine crucial efforts to win hearts and minds."