Sudanese officials have stated they will not turn over the suspects to the ICC because it does not recognize its authority. According to the principle of complimentarity, the ICC may only compliment a national court system and does not replace that system if one is open and functioning. Sudan has said it is capable of trying suspects of accused atrocities and does not need assistance from the ICC. The referral of the Sudanese case, however, was made under mandate by the United Nations Security Council in 2005, which would theoretically obligate Sudan to comply or face material breach. The prosecutor for the ICC, Luis Moreno-Ocampo, stated that "[t]he judges have issued arrest warrants. As the territorial state, the government of Sudan has a legal duty to arrest Ahmed Haroun and Ali Kushayb. This is the International Criminal Court's decision, and the government has to respect it." Human Rights Watch officials have said in comments to Agence France-Presse that the arrest warrants "shifts the burden to Sudan" to honor the UN Security Council resolution.
US President Bush has recently declared the atrocities in Darfur are genocide. And, according to the report, the Sudanese government is smuggling weapons into Darfur by disguising official planes as UN vehicles and is using government planes to conduct bombing raids.
ICC arrest warrant: Ahmed Haround, Ali Kushayb
FPA blogger, Cassandra Clifford, has background here.