The French High Court of Appeal has rejected a bid by a convicted killer to escape extradition to Italy.
Battisti has become a successful crime writer since moving to France
Cesare Battisti, who used to belong to a 1970s left-wing extremist group, is wanted in Italy for four murders.
But the former member of the radical Armed Proletarians for Communism, is still missing after failing to report to Paris police on Saturday.
France had agreed to extradite Mr Battisti to Italy but the appeal held up the process.
France currently has a warrant out for his arrest. After Wednesday's ruling, the extradition order will be complete once Prime Minister Jean-Pierre Raffarin signs a decree to send Mr Battisti back home.
Mr Battisti, who has made a successful career as a crime writer, escaped from prison in Italy in 1981 and turned up in France in 1990, where he was granted asylum by then President Francois Mitterrand.
An Italian request for his extradition in 1991 failed.
At the time, France offered sanctuary to former leftist militants from Italy who renounced their violent pasts - an offer taken up by several former guerrillas.
The BBC's Caroline Wyatt says times have changed and attacks on France by Algerian extremists in the 1990s and the events of 11 September have convinced the current government that France cannot be seen as a refuge for militants of any kind.
On 30 June this year, the presiding judge at the Paris appeals court, Norbert Gurtner, said he would favour the extradition request.
In Italy, Mr Battisti was sentenced in absentia to carrying out or helping to plan four murders in 1978 and 1979 - including those of a policeman and prison guard.
He says he was not granted a fair trial.
His case has become something of a cause celebre, with an internet petition of support attracting 20,000 signatures, including those of some prominent politicians.
Throughout the 1970s and 1980s, groups from Italy's far left and right waged violent campaigns of killings and bombings as they tried to bring down the government.
The French policy of granting amnesty to Italian leftists accused of violent crimes was based on French disapproval at Italy's policy of mass arrests and use of informants.