International aid groups fear the Sudanese government will respond by putting up more obstacles to their relief work.
Khartoum has agreed to swap prisoners and talk with Darfur insurgents.
Though largely symbolic, the law could be having lasting implications.
Witness recants testimony during start of Congo militia leader Thomas Lubanga's trial.
Critics say The International Criminal Court's move Monday to indict Sudan's president for war crimes may hamper peace.
The pending charges by the international court have put the UN on edge, as it fears reprecussions against its peacekeepers in Darfur.