Is permanent divorce reversed after doubtful marriage to second husband?
5-1-2014 | IslamWeb
Question:
Assalamo alikom, I divorced my wife three times and she became haram to me. Later on, she married a Muslim brother and consummated the marriage. However, she got divorced from her second husband. She had two witnesses but NO wali in her second marriage and now she wants to remarry her first husband (me). (Note: she didn't do that to remarry her first husband). The questions: Was her second marriage valid as she believed that wali is required only for virgin women? Can he remarry her first husband? I am worried to marry her and she is still haram for me if her second marriage was invalid, please give me fatwa which make Allah pleased with you and me.
Answer:
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 
is His Slave and Messenger.
The consent and presence of the Wali (woman's guardian) is a condition for the validity of the marriage contract according to the view of the majority of scholars; this applies to both a virgin and a non-virgin woman.
Therefore, if this marriage took place without the Wali, then it is Faasid (a defective marriage).
A marriage whose defectiveness is disputed does not make a wife who is divorced three times lawful for her first husband. One of the marriage conditions that makes the wife lawful for her first husband after three times divorce is that it is a valid marriage.
Al-Ghazaali, says in Al-Waseet, one of the books of Shaafi'i Fiqh: “A woman who is divorced three times does not become lawful for her first husband until she marries another husband a correct marriage and then he divorces her and her waiting period expires.”
According to Haashiyat Ar-Rawdh Al-Murbi’ ‘ala Zaad Al-Mustaqni’, in the Hanbali Fiqh: “A woman who was divorced three times does not become lawful for her first husband by [a marriage that is consummated through] anal intercourse, or a doubtful marriage in which the husband had sexual intercourse with her, or sexual intercourse while she is a slave woman (as if her master had sexual intercourse with her because her master is not a husband for her), or a defective marriage, as Allaah says (what means): {… until [after] she marries a husband other than him} [Quran 2:230]” [End of quote]
An-Nawawi 
said in his commentary on Saheeh Muslim: “If he has sexual intercourse with her in a defective marriage, she does not become lawful for her first husband according to the most correct opinion as he [the second husband] was not a [legitimate] husband.” [End of quote]
For more benefit, kindly refer to Fatwa 130543.
Therefore, it is not lawful for you to marry your ex-wife again until she marries another husband a valid marriage, and then he divorces her or dies; unless her marriage without a Wali was ruled as valid by a judge who adopts this view. For more benefit, please refer to Fatwa 130284.
Finally, it should be noted that one should not hasten to initiate divorce without being certain that the best solution and interest is in divorce.
Allaah Knows best.