Rwanda accuses Agathe Habyarimana, 69, of helping to plan the genocide. She denies the accusations.
Rwandan Justice Minister Tharcisse Karugaramatold the BBC that he respected the ruling, but said she should now face trial in France.
More than 800,000 Tutsis and moderate Hutus died in the massacres.
Juvenal Habyarimana, a Hutu, was killed when his plane was shot down above Kigali airport on 6 April 1994.
Within hours a campaign of violence, carried out mostly by Hutus against Tutsis, spread from the capital throughout the country.
The Hutu militias blamed the Tutsis for downing the president’s plane, although it has never been proved who was responsible.
It is widely believed that Hutu extremists and the government had long planned the genocide.