If a marriage is contracted according to a European country's civil law codes, then the husband and wife are required to abide by those civil law codes. This is because the contract that they entered into subjects them to those codes. The husband and wife are at the same time obliged to abide by the dictates Islamic Law because they are Muslims.
Regarding divorce, some people assume that Europe's civil law gives the right of divorce to the woman. This is not the case at all. Rather, it does not give the right of divorce to either spouse, but reserves that right exclusively for the judicial system. The husband cannot simply pronounce a divorce and neither can the wife.
What this means is that the husband, by entering into the civil marriage contract, waives his right to divorce by pronouncement that Islamic Law automatically grants him, and delegates that authority to the judge. This delegation of the right to pronounce divorce is permitted in Islamic Law.
We can see how far this matter is from the question of the wife being granted the right to pronounce divorce. In the civil marriage contracts of the West, the man does not have that right to divorce by pronouncement to begin with, nor does the wife. A divorce only occurs after one or both parties sues for divorce in court.
In the event that a judge grants a divorce at the behest of either or both parties according to the country's civil law, then the judge's decision is effective and the divorce has taken place. This is because the husband and wife entered into a marriage contract under that civil law. This ruling is in accordance with the resolution of the European Fatwa Council, the text of which is as follows:
The norm is that a Muslim appeals legal matters to a Muslim judge or whoever fulfils the function of a Muslim judge. However, since there is up to now no Muslim judge for Muslims living outside of Muslim lands to appeal to, it becomes incumbent upon the Muslims who contract their marriages according to the laws of those countries to abide by the ruling of divorce given by the non-Muslim judge. This is because the Muslim, by contracting a marriage under to that non-Islamic law, has implicitly shown his agreement with the consequences of doing so.
One of these consequences is that the marriage contract cannot be undone except by the judge. This can be regarded as the man transferring the right to pronounce divorce to another, which is permissible in Islamic law according to the majority of scholars. This transfer of right is upheld, even though the husband does not explicitly state it, since there is a general axiom of Islamic Law that states: "What is known by prevailing custom has the strength of what is specifically stated as a contractual condition."
Carrying out the decision of the judge – even a non-Muslim judge – is permissible in Islamic Law under the ruling of securing the general welfare and preventing harm, as well as that of preventing anarchy. This matter has been discussed by leading Islamic jurists like `Izz al-Dîn b. `Abd al-Salâm, Ibn Taymiyah, and al-Shâtibî.
And Allah knows best.