BAHAI, Chad -- Here, at this refugee camp on the border of Sudan, nothing separates us from Darfur but a small stretch of desert and a line on a map. All the same, it's a line I can't cross. As a representative of the United Nations High Commissioner for Refugees, I have traveled into Darfur before, and I had hoped to return. But the UNHCR has told me that this camp, Oure Cassoni, is as close as I can get.

Sticking to this side of the Sudanese border is supposed to keep me safe. By every measure -- killings, rapes, the burning and looting of villages -- the violence in Darfur has increased since my last visit, in 2004. The death toll has passed 200,000; in four years of fighting, Janjaweed militia members have driven 2.5 million people from their homes, including the 26,000 refugees crowded into Oure Cassoni.

Sudanese refugees from Darfur rest near a camp in eastern Chad this month. (By Alfred De Montesquiou -- Associated Press) Sudan Official Accused of War Crimes The International Criminal Court's prosecutor in The Hague outlined what he called operational, logistical and command links between Sudan's government in Khartoum and horse-mounted nomadic militias it recruited and bankrolled to carry out mass killings in the Darfur region, and he named a member of... Who's Blogging? Read what bloggers are saying about this article. FP Passport | blogging on global news, politics, economics and ideas Anaedo's Periscope Tales from the Nomad Full List of Blogs (56 links) » Most Blogged About Articles On washingtonpost.com | On the web Save & Share Article What's This? Digg Google del.icio.us Yahoo! Reddit Facebook

Attacks on aid workers are rising, another reason I was told to stay out of Darfur. By drawing attention to their heroic work -- their efforts to keep refugees alive, to keep camps like this one from being consumed by chaos and fear -- I would put them at greater risk.

I've seen how aid workers and nongovernmental organizations make a difference to people struggling for survival. I can see on workers' faces the toll their efforts have taken. Sitting among them, I'm amazed by their bravery and resilience. But humanitarian relief alone will never be enough.

Until the killers and their sponsors are prosecuted and punished, violence will continue on a massive scale. Ending it may well require military action. But accountability can also come from international tribunals, measuring the perpetrators against international standards of justice.

Accountability is a powerful force. It has the potential to change behavior -- to check aggression by those who are used to acting with impunity. Luis Moreno-Ocampo, chief prosecutor of the International Criminal Court (ICC), has said that genocide is not a crime of passion; it is a calculated offense. He's right. When crimes against humanity are punished consistently and severely, the killers' calculus will change.

On Monday I asked a group of refugees about their needs. Better tents, said one; better access to medical facilities, said another. Then a teenage boy raised his hand and said, with powerful simplicity, "Nous voulons une épreuve." We want a trial. He is why I am encouraged by the ICC's announcement yesterday that it will prosecute a former Sudanese minister of state and a Janjaweed leader on charges of crimes against humanity.

Some critics of the ICC have said indictments could make the situation worse. The threat of prosecution gives the accused a reason to keep fighting, they argue. Sudanese officials have echoed this argument, saying that the ICC's involvement, and the implication of their own eventual prosecution, is why they have refused to allow U.N. peacekeepers into Darfur.

It is not clear, though, why we should take Khartoum at its word. And the notion that the threat of ICC indictments has somehow exacerbated the problem doesn't make sense, given the history of the conflict. Khartoum's claims aside, would we in America ever accept the logic that we shouldn't prosecute murderers because the threat of prosecution might provoke them to continue killing?

When I was in Chad in June 2004, refugees told me about systematic attacks on their villages. It was estimated then that more than 1,000 people were dying each week.

In October 2004 I visited West Darfur, where I heard horrific stories, including accounts of gang-rapes of mothers and their children. By that time, the UNHCR estimated, 1.6 million people had been displaced in the three provinces of Darfur and 200,000 others had fled to Chad.

It wasn't until June 2005 that the ICC began to investigate. By then the campaign of violence was well underway.

As the prosecutions unfold, I hope the international community will intervene, right away, to protect the people of Darfur and prevent further violence. The refugees don't need more resolutions or statements of concern. They need follow-through on past promises of action.

There has been a groundswell of public support for action. People may disagree on how to intervene -- airstrikes, sending troops, sanctions, divestment -- but we all should agree that the slaughter must be stopped and the perpetrators brought to justice.

In my five years with UNHCR, I have visited more than 20 refugee camps in Sierra Leone, Congo, Kosovo and elsewhere. I have met families uprooted by conflict and lobbied governments to help them. Years later, I have found myself at the same camps, hearing the same stories and seeing the same lack of clean water, medicine, security and hope.

It has become clear to me that there will be no enduring peace without justice. History shows that there will be another Darfur, another exodus, in a vicious cycle of bloodshed and retribution. But an international court finally exists. It will be as strong as the support we give it. This might be the moment we stop the cycle of violence and end our tolerance for crimes against humanity.

What the worst people in the world fear most is justice. That's what we should deliver.

The writer is a goodwill ambassador for the United Nations High Commission for Refugees.