But how was Majdi Mustafa Nema -- better known by his nom-de-guerre of Islam Alloush -- allowed to have a visa to enter France, not least as part of the EU's Erasmus student exchange programme, to attend a leading French academic institution?
Rights groups say his story leaves the French authorities with serious questions to answer, as Syrians who took part in their country's civil war could be eyeing a shift to respectability in academia.
AFP looks at how Nema/Alloush rose to prominence in the Syrian war, became a spokesman of a Salafist group, and then sought to carve out a role as an expert in France.
Born in 1988, Nema was a captain in the Syrian armed forces before defecting, later becoming a senior official and spokesman for Jaysh al-Islam.
In June 2017, he left Jaysh al-Islam, one of the key groups opposing the rule of President Bashar al-Assad but which also stood accused of carrying out a "reign of terror" in rebel areas it controlled, especially Eastern Ghouta.
"This group controlled the checkpoints through which humanitarian aid passed for Ghouta and it took taxes as it went through," Fabrice Balanche, a geographer specialising in Syria at the University of Lyon, told AFP.
Nema's Facebook account says he attended the ELTE public university in Budapest in 2018 and then obtained a diploma in political science and international relations from the Aydin University in Istanbul.
His aim was to "recycle himself and become an agent of influence with a university background to be more credible," Balanche said.
'No due diligence'
According to judicial sources, Nema has been in France since November 2019.
He was registered as a student at the IREMAM research institute for the Arab and Muslim world at the Aix-Marseille University in southern France, operated in cooperation with France's CNRS national academic research centre.
According to the institute, Nema had a visa issued by the French consulate in Istanbul.
The French foreign ministry confirmed that a short-stay visa had been issued to Nema "on the basis of a complete application and after asking the relevant ministerial services."
Richard Jacquemond, IREMAM's director, said it was common for young Arabs who had been deeply involved in the uprisings against authoritarian regimes to later try to gain a foothold in academia.
He told AFP that he was unaware of Nema's past, adding that because the process of obtaining a French visa is so tough, one could assume "that the consulate services have done their work."
He also said such people often have "very interesting profiles as they can bring us first-hand experience."
But Chris Doyle, director of the Council for Arab-British Understanding (Caabu) in London, said Nema was rejected by a prominent British University and expressed bewilderment at the lack of checks by France.
"There was seemingly no due diligence (in France) and I can't see why," Doyle told AFP.
"How many other people like him are trying to do the same sort of thing, trying to get into the EU and trying to start life again as academics, but have a very shady background in terms of what they have done on the battlefield?" he said.
Jaysh al-Islam is suspected of involvement in the December 2013 kidnapping of Syrian activist Razan Zaitouneh, her husband Wael Hamada and two colleagues, Samira Khalil and Nazem Hammadi. They are still missing.
Zaitouneh was one of the most prominent civil society figures in the uprising against Assad, and in 2011 she was awarded the prestigious Sakharov prize for human rights along with other activists.
The Salafist group, which has taken part in Syria peace talks in Astana and Geneva, has denied any involvement in the kidnapping of the so-called Douma Four.
Rights groups including the International Federation for Human Rights (FIDH) filed a criminal complaint in June last year against members of Jaysh al-Islam for alleged crimes.
It was the FIDH that signalled the Nema's presence in France to judicial authorities on January 10, after painstaking research into the Jaysh al-Islam hierarchy.
The fact that someone who had a public role at a Salafist group was allowed to obtain a visa "is surprising for us to say the least," FIDH legal coordinator Clemence Bectarte said.