Article L813-1 of the French Code governing the entry and residence of foreign nationals and the right of asylum
If, during a check referred to in article L. 812-2, it appears that a foreign national is unable to prove his right to move or reside in France, he may be detained for the purposes of verifying his right to move or reside on French territory. In this context, the foreign national may be taken to a police or gendarmerie station and held there by a judicial police officer from…