Tens of thousands fled the region following violence last year
Judges in The Hague have ruled that the boundaries of Sudan's disputed oil-rich region of Abyei should be redrawn.
The region is claimed by both north and south Sudan, and became a flashpoint in a long-running civil conflict.
The Permanent Court of Arbitration decided not to accept the boundaries drawn up as part of a 2005 peace deal, which were rejected by the north.
It ruled that the eastern and western borders of Abyei should be redrawn, reducing the size of the region.
The effect of the ruling on the region's northern boundary is not immediately clear.
Fears of violence
The Hague court decided on where Abyei's borders lie rather than who owns the land.
Analysts say the size of Abyei is crucial as its inhabitants will be asked in a referendum in 2011 whether they want to be a part of north or south Sudan - and are likely to opt for a union with the south.
The north had rejected the boundaries proposed by the 2005 peace deal because they were thought to make the region too big.
UN peacekeepers have beefed up their presence in Abyei amid fears that a controversial ruling could spark violence.
The issue was referred to The Hague court last year after clashes broke out in Abyei town, killing about 100 people and forcing tens of thousands to flee.
The main parties in north and south Sudan have pledged to abide by the court ruling.