A French appeals court has rejected a request to reopen an investigation into the shooting down in 1994 of a plane carrying the then-Rwandan President Juvenal Habyarima.
The incident sparked the Rwandan genocide in which 800,000 people were killed.
The inquiry was dropped in 2018, but Habyarimana's widow, Agathe, and the families of other victims had appealed against the decision.
But it may not be the end of the case, as civil parties have already said they will move to a higher court, the AFP news agency reports.
Relations between the France and Rwanda have been turbulent ever since a French judge in 2006 accused several close associates of current Rwandan President Paul Kagame of being behind the assassination of Habyarimana.
At the time Mr Kagame was the leader of a Tutsi rebel force which was fighting the Hutu-dominated government.
He has always said that Hutu extremists shot the missiles that brought down the president's plane.
Under current French President Emmanuel Macron, political relations have improved.