Kacy Plathey, convicted of a string of crimes and jailed in the Saint-Quentin-Fallavier prison in Isere, southern France, was ordered to be held 45 days in a punishment cell after a dispute with a prison guard in January 2009.
The cell had been burnt out by a previous detainee and was "completely destroyed and insanitary with an atmosphere that was highly unpleasant", the court found.
Plathey stayed for 28 days -- locked down for 23 hours out of each 24 -- in conditions described by a visiting senator as "at the limit of suffocation."
Court judges said the conditions "were an attack on human dignity and constituted degrading treatment.
Awarding the plaintiff €9,000 for moral distress, the court also found in favour of Plathey's complaint that he had been unable to contact a judge who could have ruled on the conditions of his detention in the cell before his punishment period ended.
His lawyer Patrice Spinosi said it was the fourth time this year France had been condemned by the court for degrading treatment of prisoners.