France's highest appeals court has authorised judges to proceed with an investigation into assets held in the country by three African leaders.
The anti-corruption group Transparency International has accused the three of using African public funds to buy luxury homes and cars in France.
A Paris court halted the lawsuit last year, saying Transparency could not act against foreign heads of state.
The three leaders, one of whom is now dead, had denied wrongdoing.
They are Denis Sassou-Nguesso of the Republic of the Congo and Teodoro Obiang Nguema of Equatorial Guinea, as well as the late Gabonese leader, Omar Bongo.
Transparency estimates the total value of the three leaders' estates in France at 160m euros (£140m, $223m).
Quoting French police investigations dating back to 2007, it said President Obiang owned vehicles worth more than 4m euros, the late Bongo and his relations had 39 homes, and Mr Sassou Nguesso and his relations held 112 bank accounts.
Investigations found that Bongo's wife Edith had bought a Daimler Chrysler car with a cheque drawn on a Gabonese government account in France, Transparency added.
"For the first time in France, a lawsuit by an anti-corruption association acting for the interests it aims to defend has been judged admissible," the anti-corruption group said in a statement welcoming the ruling.
It hoped the funds allegedly stolen would eventually be recovered.
The case followed a 2007 French police investigation which had found the leaders and their relatives owned homes in upmarket areas of Paris and on the Riviera, along with luxury cars including Bugattis, Ferraris and Maseratis.
Transparency, along with rights group Sherpa, had argued that it was not possible that the men and their entourages had bought the assets through their legitimate salaries.
When a French magistrate ruled in May 2008 that the "ill-gotten gains" case was admissible in a French court, representatives of the leaders contested the ruling.
They argued that, as civil society activists, Transparency had no right to act as plaintiffs against heads of state.
Transparency appealed in turn and its action was upheld on Tuesday.
Gabon and Republic of Congo are former French colonies.
Omar Bongo - who was Africa's longest-serving leader - died in June 2009 but members of his family were also named in Transparency International's case.