The case, the first of its kind in France, targets 15 suspects, including the group’s co-founder.
“Here are the Internet terrorists,” their lawyer Remy Josseaume told the court sarcastically in the southern city of Rodez.
“It is hypocritical to put these people on trial while there are many products that inform drivers where radars are positioned and they are legal,” he said.
The suspects face charges of helping motorists and motorcyclists avoid speeding fines.
Eight of them also face charges of insulting police officers by referring to them by unflattering bird names on the site.
The Facebook group “Which Tells You Where The Police Are In (the southern French town of) Aveyron” was created in 2012 and has more than 10,000 members.