The ICJ may be little known, but it is becoming an increasingly important international forum.
The ICJ ruled in 2004 that the separation barrier between Israel and the occupied West Bank was illegal, but it is still standing.
The ICJ adjudicates on disputes between states and its rulings are binding.
This is the second time that Serbia has faced accusations of genocide at the ICJ.
If so, the venue will be the International Court of Justice (ICJ) at The Hague.