Abyei notes

The dispute between South Sudan and Sudan over the Abyei region was the most volatile aspect of Sudan’s 2005 Comprehensive Peace Agreement (CPA), according to the European Coalition on Oil in Sudan (ECOS) in a 2008 report, and after South Sudan's secession in July 2011 the administration and authority issues between South Sudan and Sudan in Abyei were in contention once again. The dispute over control of the Abyei region remains unresolved as of mid 2012.

=The conflict=

Comprehensive Peace Agreement of 2005
The 2005 Comprehensive Peace Agreement (CPA) between South Sudan and Sudan created the Abyei Boundary Commission, which issued a "final and binding" ruling on Abyei’s boundary in July of that year, according to the Enough Project. Sudan's ruling National Congress Party (NCP) rejected the ruling, however, and a three-year stalemate ensued until the dispute erupted into violence in May 2008, when Sudanese armed forces razed Abyei town and forcibly displaced an estimated 60,000 people - the majority of the town’s population. Following weeks of negotiations, representatives of the NCP and South Sudan's Sudan People's Liberation Army (SPLA) agreed to refer the boundary dispute to international arbitration.

Ruling of the international tribunal in 2009
On July 22, 2009, a Hague-based ad hoc  international tribunal, operating under the rules of the Permanent Court of Arbitration (PCA), rendered its final ruling in the Abyei case. The PCA ruling largely delinked the issue of oil wealth-sharing from Abyei’s boundaries by placing the majority of oil producing areas and oil infrastructure outside the Abyei Area, according to Concordis International.

The Award considerably reduced the extent of the Sudanese Abyei area compared to a previous decision in 2005, according to the Hague Justice Portal.