Media nouveau has been on trial by media since September 2014 when a man claiming to be a social media expert was arrested after posting a video online showing him using a Snapchat account and Twitter to distribute content.
The trial by the French media watchdog is expected to last for two weeks.
The man is being tried for a string of offences including fraud and aiding a crime.
The court is considering whether the man acted illegally and whether he should be held accountable for any breaches of French law.
He is also accused of spreading false information about the number of followers he has on social media sites, including Facebook.
The accused man was arrested in August 2016 on suspicion of promoting a crime after posting an image of a woman being tortured in a video on his Snapchat account.
A spokesman for the media watchdog, Stephane Vercauteren, said: “There’s a big gap between the content on social networks and what they say on the websites.”
“The law says that social media is an open forum for the dissemination of information, and we are investigating this case very carefully.”
He said the case was being prosecuted on the basis of the French Criminal Code which makes it an offence to disseminate false information on social platforms.
A French prosecutor in Lyon said the accused had a long history of using social media and the video showed a man in a black T-shirt carrying out “extremist” actions.