The court in Aix-en-Provence threw out Cédric Herrou’s appeal against a suspended 3,000-euro fine, replacing it with a four-month suspended jail term for helping about 200 migrants, mostly Eritreans and Sudanese, enter France and lodging them in a disused holiday camp owned by the SNCF rail company.
It also reversed a not-guilty verdict on illegal occupation charges and ordered him to pay the SNCF 1,000 euros in damages with interest.
Prosecutors had called for an eight-month suspended prison sentence.
Herrou, 38, is a member of a solidarity group in the Roya valley, near the Italian border, and has been arrested six times this year.
“It is the role of the citizen to take action when the state fails in its duty,” he said before his appeal was heard, alleging that 15 people have died trying to cross the border in the valley.
He will appear in court again soon.
He was arrested on 26 July while accompanying 150 migrants to the station of the Riviera resort of Cannes.