Is a Muslim man's marriage to a Christian woman valid if it takes place in the presence of his mother and two witnesses, with the knowledge and consent of her guardian even if he is not present, and without the contract being documented in court, given the impossibility of the guardian's presence and the independence of children in Europe?

The mere knowledge and consent of the guardian (wali) are not sufficient for the validity of the marriage (nikah (definition)). Rather, his presence or his authorization of a proxy is essential. Otherwise, the marriage is invalid and must be renewed according to the Sharia (definition) conditions, unless a judge who holds that view rules it to be valid.