The International Criminal Court (ICC) has overturned the conviction for war crimes and crimes against humanity of former Democratic Republic of Congo Vice-President Jean-Pierre Bemba.
He was accused of failing to prevent his rebels killing and raping.
But a judge has now said he cannot be held responsible for their actions.
Christine Van den Wijngaert also said the judges in the 2016 case had failed to take into account his attempts to stop the crimes once he was made aware they were taking place.
The decision to overturn the 18-year sentence was greeted with cheers from his supporters in the gallery.
But human rights group Amnesty International said it was a "huge blow" for the victims of a "horrifying campaign of rape and sexual violence", as it called on the authorities to redouble their efforts to prosecute those who had carried it out.
ICC prosecutor Fatou Bensouda described the ruling as "regrettable and troubling".
More than 5,000 survivors took part in the proceedings against Bemba, said Amnesty's head of international justice, Solomon Sacco.
"For these brave individuals, as well as thousands of other victims in CAR, the pursuit of truth, justice and reparations will continue," he added.
Who is Jean-Pierre Bemba?
- A well-connected businessman and the son of prominent Congolese businessman Bemba Saolona
- 1998: Helped by Uganda to form MLC rebel group in Democratic Republic of Congo
- 2003: Becomes vice-president under peace deal
- 2006: Loses run-off election to President Joseph Kabila but gets most votes in western DR Congo, including Kinshasa
- 2007: Flees to Belgium after clashes in Kinshasa
- 2008: Arrested in Brussels and handed over to ICC
- 2010: Trial begins
- 2016: Found guilty of war crimes and crimes against humanity
- 2018: Conviction overturned on appeal