The situation in Darfur is a threat to the international system. The situation threatens international peace and security, not to mention the multiple human rights issues involved. Humanitarian intervention is paramount to solving the crises in Darfur. If negation is not possible, military intervention would have to be considered for protection.
The Darfur situation has very little impact on the stability of the international system. Although many would say that intervention by other forces is necessary, the situation hasn't escalated to levels that would threaten outsiders. If militant forces were to rise to levels of, say, terrorist groups in the Middle East like Al Qaeda, then perhaps the situation would then become threatening.