Article 749 of the French Code of Criminal Procedure
In the event of voluntary non-compliance with one or more fines imposed in criminal or correctional cases for an offence punishable by imprisonment, including in the event of voluntary non-compliance with tax or customs fines, the sentence enforcement judge may order, under the conditions set out in this Title, a judicial restraint consisting of imprisonment, the duration of which is set by this magistrate within the limit of a maximum…