Significantly, the United Nations has embraced our responsibility to intervene in countries where such atrocities are being committed.
And the complement to this is the principle of universal jurisdiction, which allows for prosecution in any country of certain serious offences wherever and by whoever they were committed.
It is our moral duty to ensure that there is no hiding place for those suspected of the most serious international crimes.
Britain will continue to take action to prosecute or extradite suspected war criminals – regardless of their status or power.
This is why the UK was among the first countries in the world to put in place legislation providing for universal jurisdiction over torture, hostage taking and grave breaches of the Geneva Conventions.
Without universal jurisdiction the Afghan warlord Faryadi Zardad, who had fled to London on a fake passport, would not have been brought to justice for a merciless campaign of terror in his homeland.
Britain will always honour its commitment to international justice. The police here remain ready to investigate cases; the Crown Prosecution Service to bring them; the courts to hear them.
But the process by which we take action must guarantee the best results.
The only question for me is whether our purpose is best served by a process where an arrest warrant for the gravest crimes can be issued on the slightest of evidence.
As we have seen, there is now significant danger of such a provision being exploited by politically-motivated organisations or individuals who set out only to grab headlines knowing their case has no realistic chance of a successful prosecution.
Men and woman can then be held in prison on the basis of 'information', when the serious nature of such cases means that in any event they can only proceed to prosecution with the consent of the Attorney General.
There is already growing reason to believe that some people are not prepared to travel to this country for fear that such a private arrest warrant – motivated purely by political gesture – might be sought against them.
These are sometimes people representing countries and interests with which the UK must engage if we are not only to defend our national interest but maintain and extend an influence for good across the globe.
Britain cannot afford to have its standing in the world compromised for the sake of tolerating such gestures.
There is a case now, therefore, for the evidential basis on which arrest warrants can be allowed to be tougher and for restricting the right to prosecute the narrow range of crimes falling under universal jurisdiction to the Crown Prosecution Service alone.
Such a modification requires legislation. It is also extremely controversial in some quarters, involving as it does the long-standing right of private prosecution. So we will consult on our proposals to improve the system, with my full intention to legislate as soon as possible.
Britain remains absolutely committed to upholding the principles of universal jurisdiction. And where individuals or organisations have genuine grounds for allegations that any of the offences in question have been committed we encourage them to bring forward evidence to the police.
But by bringing the risk of arrest into closer alignment with the risk of prosecution, our system of universal jurisdiction can be stronger. For it would be clear that we only bring cases based on evidence of sufficient strength to convince the Director of Public Prosecutions that there is a credible case.
With this approach, I am confident that an amendment on better enforcement of existing legislation will serve to enhance Britain's status in the eyes of international law, world opinion and history.