Félicien Kabuga, one of the last key suspects in the Rwandan genocide, lost an appeal on Wednesday to be released under court supervision.
The UN's International Criminal Tribunal for Rwanda (ICTR), which issued an international arrest warrant for Kabuga in 1997 "has a very strong claim over this case," Clark told RFI.
The tribunal, which closed in 2015 after indicting over 90 genocide suspects, including Kabuga, has been replaced by the International Residual Mechanism for Criminal Tribunals at The Hague.
Once one of Rwanda's richest men, Kabuga "benefitted from a lot of protection and complicity," says Patrick Baudouin, a lawyer and honorary president of the International Federation of Human Rights.
After Wednesday's hearing, the Paris appeal court will have 15 days to deliver its ruling, which Kabuga can still appeal.
