Bahar Idriss Abu Garda gave himself up last year
The first Darfur war crimes suspect to face international judges has had the charges against him dropped.
Rebel leader Bahar Idriss Abu Garda, who gave himself up last year, had been accused of planning the killing of 12 African Union peacekeepers in 2007.
But International Criminal Court (ICC) judges ruled that there was not enough evidence to support a trial.
Last week, the ICC said charges of genocide against Sudan's President Omar al-Bashir could be resubmitted.
Mr Bashir is already wanted for war crimes.
Mr Abu Garda was a senior member of the Justice and Equality Movement (Jem) - the main rebel group fighting militias that many suspect are government backed.
He left Jem in 2008 and formed his own group, the United Resistance Front.
Mr Abu Garda has always denied being part of the attack on the peacekeepers.
He told the court during a pre-trial hearing last year that he had denounced the attack at the time as serving the interests only of the Sudanese government.
On Monday, the judges said in a statement: "The chamber declines to confirm the charges against Mr Abu Garda."
But they added that prosecutors were still free to bring more evidence which could yet lead to prosecution.
The UN estimates that 300,000 people have died in Darfur since the conflict began in 2003.
Some 2.7 million have been displaced.