French police on Wednesday arrested a leading figure in conspiracy circles over the kidnapping of an eight-year-old girl in April, as he returned to the country on a flight from Singapore.
Remy Daillet, who was travelling with his pregnant partner and three children, was detained on arrival at Paris Charles de Gaulle airport, the public prosecutor in the eastern city of Nancy, Francois Perain, said.
The kidnapped girl, identified only by her first name Mia, was taken in mid-April from the home in eastern France of her grandmother, her legal guardian, by several men employed by Mia's mother.
She was found a few days later in a squat in Switzerland, in the care of her mother who had lost custody of her. She was returned to her grandmother.
Investigators believe the abduction may have been organised by extremists led by Daillet who believe that children in care are unfairly taken from their parents.
Shortly after his arrival in Paris he was transferred to Nancy for questioning by an investigating magistrate.
Daillet, 54, and his family were arrested at the end of May on the Malaysian holiday island of Langkawi after their visas expired. Kuala Lumpur then began the process of deporting them to France.
But the process was delayed Sunday during a stop off in Singapore where Daillet's partner, Leonie Bardet, was hospitalised. His lawyers argued that she was unfit to travel.
Ten individuals, including Mia's mother who was no longer allowed to see her daughter alone, have been charged over the child's abduction.
Seven of them are already in preventive custody.
Daillet is known to police as a proponent of extremist conspiracy theories and of a populist takeover of the state.
After the abduction, Daillet posted a video in which he said that his organisation "returns children kidnapped by the state to parents, at their request. There was absolutely no kidnapping".
In earlier videos, he has supported the idea of a coup d'etat and voiced opposition to taxes, vaccines, and 5G and masks.
French prosecutors in April issued an international arrest warrant for Daillet, who had been living in Malaysia for several years. His detention over his residency status accelerated the deportation process.
Daillet was a regional leader of France's centrist MoDem party before being dismissed from the party in 2010.