All seven are suspected of having been involved, to various degrees, since 2012 – but mainly during 2013 - in a network recruiting radicalised young men to fight in Syria.
Amongst them, Salim Benghalem, 35, who is the subject to an international arrest warrant since May 2014, is the highest-profile suspect.
Benghalem, who is believed to be in Syria at the moment, is tried in absentia. He is accused to be linked to the attacks on the Charlie Hebdo satirical magazine and a Jewish supermarket in Paris last January. The killings claimed 17 victims, including a policewoman.
According to intelligence sources, Benghalem is one of the top French recruiters in the IS chain of command. He also appeared in an IS video last February.
French daily newspaper Le Monde reported that Benghalem was the target of the French air strikes on the Syrian city of Raqqa in October.
Benghalem is also suspected to have been the French IS member guarding the four French journalists kidnapped between June 2013 and April 2014 in Syria.
Along with him in Syria was another French jailer, Medhi Nemmouche, who was involved in the shooting in the Jewish Museum in Brussels in May 2014.
Another of the accused men spent a year and a half in Syria fighting for several groups, including an Al-Qaeda franchise. Abdelmalek T., 26, is suspected of recruiting four of his co-accused.
“I’ve helped them to cross the border,” said the French-Algerian citizen on Tuesday, denying his involvement in the fighting or of having participated in any military training.
In contrast, Younes C. has never been to Syria. He is accused of having been a facilitator in recruiting for Abdelmalek T.
Co-defendants Paul M., Karl D., Karim H. et Medhi I., are said to be friends since their school days. They are from the same neighbourhood and are believed to have gone to the same mosque. The court heard that they spent between 10 days and two months in Syria and only is reported to have fought for IS in Syria.