The legacy of Iraq is that the world stands by while Darfur burns

I once spoke to a journalist who had covered the war in Bosnia in the early 1990s. He said that he and his colleagues kept heading into harm's way, because they believed that once the world knew of the horrors they had witnessed, the world would be stirred to act. They filed their reports and waited. Soon enough, they understood. The world knew what was going on - and yet it did nothing. For some of those reporters, this experience broke their faith in the power of journalism. For others, it broke their faith in their fellow human beings.

I suspect the aid workers and United Nations staff who signed a collective statement on the plight of Darfur in January are going through a similar heartbreak right now. Fourteen different UN humanitarian bodies, including the World Food Programme and the World Health Organisation, issued an unprecedented cry of despair. They explained that their workers had "effectively been holding the line for the survival and protection of millions, [but] that line cannot be held much longer". Under attack themselves, these UN workers could no longer reach the people they sought to protect and feed. "In the last six months alone," they wrote, "more than 250,000 people have been displaced by fighting, many of them fleeing for the second or third time. Villages have been burnt, looted and arbitrarily bombed and crops and livestock destroyed. Sexual violence against women is occurring at alarming rates. This situation is unacceptable."

I'm sure that when they drafted that message, they believed the world would stir and come to their rescue. Surely it could not ignore such a stark, desperate plea from those whose only motive is to save lives?

Well, now they know. The message came and went, reported here and there, posted on the odd website and comprehensively ignored. The humanitarians of Darfur have learned the lesson of the old Bosnia press corps: that the world might know, and know in great detail - but still the world does nothing, or waits until it's too late.

First blame lies of course with the government of Sudan, which UN human rights investigators this week accused of "gross and systematic" abuses, orchestrating and participating in a campaign of violence that has seen, at a conservative estimate, 200,000 people killed and 2 million displaced. Officially, this has been done in the course of a civil war against rebels in Darfur, who are guilty of their own atrocities. But the UN human rights council was quite clear: the "principal pattern" was of violence committed by the Sudanese government and its allies in the Arab Janjaweed militias.

Why can it not be stopped? The answer reveals much about the state of our world, the limitations of power and the extent to which the liberal interventionist vision articulated by Tony Blair during the Kosovo war in 1999 - of a world in which states could no longer murder their own people with impunity - lies in shreds.

It's not as if the international community has done nothing. In August last year the UN passed resolution 1706, agreeing to upgrade the small African Union force of 7,000 troops that was attempting to police Darfur - a territory nearly the size of France - with a UN deployment of 22,500. Such "heavy support", in both personnel and hardware, would have made a vital difference, standing between the Khartoum-backed predators and their Darfuri prey.

Trouble is - and here's a surprise - the predators don't want that force to come in. And this has to be a "consensual" deployment: it can't happen without the permission of those who are to be restrained. It's as if the police knew that terrible crimes were going on at number 73 - but were forced to stand outside, doing nothing, because the man of the house wouldn't let them in.

Omar al-Bashir, Sudan's president, is not quite as crude as that. If the pressure is sufficient, he tends to say yes to the requests of the international community - only to say no later, when the attention of the world's capitals has moved on. Bashir has turned saying no into an art form, constantly refusing UN and other officials access to refugee camps, townships and villages. Jody Williams and her team of UN human rights investigators were forced to do their work from across the border when the Sudanese authorities denied them a full set of entry visas.

Back in the prelapsarian days of 1999, when Tony Blair went to Chicago to evangelise for liberal interventionism, the response to this closed door would have been to suggest that the rest of the world, led by the west, should bust its way in. But that was before the calamity of Iraq, which has tainted for a generation the Blairite doctrine of muscular humanitarianism. So no one talks seriously about military action against Khartoum now, not least because Bashir's government is an Islamist one - and a western war against such a regime would look uncomfortably like confirmation of the clash of civilisations that both Blair and President Bush insist does not exist.

Claiming to be the victim of some western vendetta against Islam also suits Bashir, but it is bogus. For one thing, Bashir's Darfuri victims are themselves Muslim. But, more importantly, those seeking to restrain him and his Janjaweed militias are hardly the hated west - they are the African Union. It is the AU which has been impeded, harassed and attacked, and whose expansion Bashir resists. Indeed, the hybrid UN force he is currently barring would be overwhelmingly African and Asian, drawn from mainly Muslim states. The first batch of UN troops, already on standby, is from Rwanda.

But force is not the only pressure. London is pushing for narrowly targeted sanctions, aimed at Sudan's ruling elite, hitting the companies they own and the luxury goods they covet. That, combined with a no-fly zone and an arms embargo covering all Sudan - not just Darfur - could, say its backers, force Bashir to back down. If neighbouring Arab states put pressure on the rebel groups, the result could be a ceasefire and an end to the terrible violence.

Yet even that course of action seems too much for the international community. China won't sign up, because it relies on Sudanese oil and sells arms to Khartoum. Some African and Asian states have grumbled that Sudan is being unfairly singled out.

More importantly, perhaps, there is little or no pressure from public opinion. That's partly because there has been none of the intensive media coverage that triggered the drumbeat for action in Kosovo, for example. The left, who one might expect to rise in fury at the mass murder and oppression of a black African population, has also kept its distance. That might be because it suspects those demanding action on Darfur are driven by an anti-Islamist agenda, or because it fears that "action" would translate into an Iraq-style invasion.

Those are some of the reasons why the world has done nothing; perhaps there are others. But the fact of it still stains our world. At the end of this month, leaders will gather to celebrate the 50th anniversary of what became the European Union. They will make fine speeches, declaring that after the horrors of the second world war the only moral course was "never again". If those words reach all the way to Darfur, how hollow they will ring.

By Jonathan Freedland