All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
If the conditions of the validity of marriage are fulfilled, the most important of which are the presence of the bride’s wali and witnesses, then the marriage contract is valid. Please refer to fatwa 83629. It is adequate for the husband to utter the words of divorce for it to take effect; there is no need for having witnesses.
Registering the marriage contract for the purpose of documentation is not among the conditions for the validity of a marriage contract in the sharee'ah; however, it is better to register it for the preservation of rights and to avoid potential disputes in the future.
Hence, since registering the marriage contract is not obligatory in the first place, the husband is not obliged to give the marriage certificate to his ex-wife for a greater reason, especially given that she agreed on conducting the marriage contract in this office whose marriage certificates bear no legal weight, as you have mentioned. However, this must not be a source of dispute between you. If she needs an official divorce certificate so that she can remarry in the same office where your marriage was conducted and she fears that she would not be able to do so without having a divorce certificate proving that divorce has taken effect, which is a justifiable reason, then you should help relieve her from this burden and register your divorce in the same office in which you had registered your marriage so that she would be able to conduct her new marriage contract therein if she wishes; thus, you can give her what she wants and spare yourself any harm at the same time. You should know that you are legislatively obliged to give her all the due rights to which she is entitled. Please refer to fatwa 84811.
We would like to point out that one of the most important conditions to the validity of the marriage contract in Islam is the presence of the bride’s wali; if a marriage contract is conducted in the absence of the wali, it is declared defective, unless declared valid by the authority of the ruler, as scholars advised. Please refer to fatwa 130284. If this woman is Muslim and had no Muslim wali and the imaam of the mosque acted as her wali in the marriage contract, then it is valid. The same ruling applies if she was Christian or Jewish and her wali refused to marry her off to a suitable (Muslim) suitor. Based on the view that such a marriage is defective, once it is consummated, the same legal effects and implications of a valid marriage apply; the woman is obliged to observe ʻiddah in case of divorce or death, the children born of such a marriage are attributed to the husband, and the woman is entitled to the dower as underlined in fatwa 86603.
For further benefit, please refer to fataawa 92478 and 195979.
Allaah knows best.