Is civil divorce valid for Muslims?

Muslim practising women very often ask us what they can do when their husband don’t fulfill their rights towards them or when they have a non-islamic behaviour and they don’t want to grant them divorce. I would like to know your opinion about the following points: 1) May civil divorce granted by a french non-muslim judge considered as equivalent to a separation (tafreeq) granted by a Muslim Qadi if the reason for divorce is islamically valid? 2) In that case, who can decide if the reason for divorce is valid or not and how? 3) If husband and wife married only religiously and the imam who performed the marriage is available, has he the right to pronounce separation? 4) If this imam is no more reachable who can pronounce the separation between husband and wife? I am very keen to read your answer, so many women here are facing real difficulties with their husband. Jazakumullah khairan Was salam alaikum wa rahmatullah wa barakatuh