Article L321-2 of the French Code governing the entry and residence of foreign nationals and the right of asylum
The administrative ban on entry is the subject of a written decision issued after a non-adversarial procedure. Reasons shall be given for the decision, unless this is contrary to considerations of national security.If the foreign national has entered France when he or she has not already been notified of the decision to impose an administrative ban on entry, he or she shall be notified of this decision on French territory.