The UN tribunal in the Hague found a Croatian journalist and a Croatian security official guilty of contempt on Friday for making public the identity of a protected witness and his testimony.
The court said it had decided to fine the two men €15,000 each. The contempt charge carries a maximum sentence of seven years in prison or a €100,000 fine.
Ivica Marijacic was editor-in-chief of the Zagreb-based weekly Hrvartski List, and Markica Rebic is the former head of Croatia's Security Information Service.
Mr Rebic provided Mr Marijacic with the identity and testimony transcript of a witness who testified in 1997 in the war crimes case against General Tihomir Blaskic, wartime Croat militia commander in central Bosnia.
Mr Marijacic then published an article in 2004 based on the testimony entitled "World Exclusive - the first in the world to publish the secret document which shows Carla del Ponte's plot against Croatia". Ms Del Ponte is the tribunal's chief prosecutor.
The court said the witness was Dutch army officer Johannes van Kuijk. It noted that no harm was done to him as a result of the disclosure of his identity and his testimony but said the court had to make sure its orders were respected.
Four other Croat journalists are also accused of contempt for publishing the identity of another protected witness in the Blaskic trial.