A Swiss court has ruled that the assets of Mobutu Sese Seko, former leader of Zaire, now the DR Congo, who died in 1997, be returned to his family.
The court rejected an appeal to extend a freeze on assets worth more than $6m that are held in Swiss bank accounts.
Switzerland had repeatedly blocked the release of the funds, which were said to have been gained illegally.
But the court said the Democratic Republic of Congo had waited too long to seek the return of the money.
The appeal was brought by Mark Pieth, a criminology professor at Basel University.
He described the court's decision as a "harsh setback" for DR Congo, and for all those who had sought the return of the money.
Mobutu seized power in Congo in 1965 and changed its name to Zaire in 1971.
He governed for nearly 32 years, living in extreme luxury whilst most people lived in poverty. He was overthrown in 1997 by Laurent Kabila, the father of DR Congo's current President Joseph Kabila.
Mobutu died a few months after his overthrow while in exile in Morocco.
The Swiss banks blocked his accounts, starting years of legal wrangling.
The DR Congo government said the money had been stolen.
But Swiss prosecutors said the DR Congo authorities took too long to ask for the return of the money, under the statute of limitations.