Finally, a line has been drawn in the sand. Since coming to power in 1989, President Omar al-Bashir has amassed a catalogue of atrocities. The ICC doesn't have jurisdiction for crimes committed before 2002. But yesterday the court showed its purpose: despots cannot hide behind state sovereignty to exterminate their own citizens.
I have heard hundreds of witnesses testify. They have a common demand: the policy of rape and murder in Sudan must be stopped. Tired of failed peace talks, they see justice as the only way to compel the government of Sudan to imagine a peaceful future. The cheer from the Darfuri refugees outside the Sudanese embassy in London as the arrest warrant was announced yesterday represented nearly six years of hopeful campaigning.
Justice and prospects for long-term peace will exact a short-term price. Al-Bashir told the ICC to eat their warrant. Khartoum has started to expel aid workers and Salah Abdallah "Gosh", the head of Sudanese security and intelligence, said he will amputate the arms and cut off the heads of anyone co-operating with the ICC.
Also in danger is the agreement between the north and south of Sudan that in 2005 ended more than 20 years of bloody civil war.
The other peace process, between Darfur and the government of Sudan, was only recently reignited and is barely flickering. The rebel groups have said they cannot have peace if it means sweeping justice under the carpet.
They understand that Sudan should not be governed by committing atrocity, and even offered to hand over their own members.
But that rule of law may be denied. Britain and France are so concerned about Khartoum's reaction that they are considering asking the UN Security Council to suspend the ICC proceedings.
The arrest warrant is the first serious point of leverage the international community has had in five years. It should not be squandered.
Strict conditions should be applied before there is any slackening of the ICC proceedings. A genuine political process, free and fair elections and disarming of the Arab militias will be a good start. And any compromise should only be in regard to extending the investigations to others in the regime.
James Smith is executive director of the Aegis Trust, a genocide prevention organisation