Is it permissible for a fasiq man to act as wali for the solemnization of his daughter?
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions, and all those who follow his footsteps until the Final day.
Wali or in Arabic al-Wali (الوَلِي) lexically means “near or close by”. It is stated as “walyyahu, walyan” which means near or in its proximity. And “wali al-Amr”, when one is dealing with him and “Tawalla al-Amr” which means he is appointed.
The terminology, al-Wilayah is used as the highest leader, qadi, army and others. There are various meanings for the word wali or wilayah, it also means a proxy or representative or guardian that is likened as the wali in someone’s lineage, proxy in inheritance division and others. 
Furthermore, the other meaning al-Wilayah is it is the antonym of al-A’dawah, of which it originally means love and closeness. While the meaning of al-A’dawah is hatred and distance. 
Whereas wali in marriage is a person who determines the validity of the solemnization (marriage). The solemnization is invalid when he is absent. A wali can be the father, a person who is bequeathed, a close family member (al-Qarib al-Ashib), a person who freed a slave, a ruler and a king. 
The word fasiq originates from the word ‘’. Ibn Manzur stated: Al-Fasiq is iniquity and neglecting the commandments of Allah Azza wa Jalla and leaving the road of the truth. 
The term fasiq means a person who commits a major sin or continuously or always committing minor sins. 
Imam al-Syaukani cited the opinion of Imam al-Qurtubi who said: “The fasiq usually used in the shariah is: (An act that causes) a person transgressing Allah SWT limitations of obedience towards Him. Sometimes the action can be considered as an act of disbelief or sinful act.” 
This is as stated in a hadith of the Prophet PBUH who said:
سِبَابُ الْمُسْلِمِ فُسُوقٌ، وَقِتَالُهُ كُفْرٌ
“Abusing a Muslim is Fusuq (evil doing) and killing him is Kufr (disbelief).” 
Ibn Battal when commenting on this hadith said, abusing another Muslim with words is prohibited, for the dignity of each Muslim is protected (prohibited from being violated), the same as it is prohibited on his life and property. An Islamic legal maxim states:
الأَصْلُ بَرَاءَةُ الذِّمَّةِ
“The origin of a person’s dignity is pure (free from any accusations and burdens).” 
The requisites for marriage (solemnization) as it is known are five. One of these requisites is for the presence of a wali. The presence or attendance of a wali is obligatory during the aqad (for the solemnization).
The author of the book al-Fiqh al-Manhaji  said: A woman is impermissible to be married, perform the marriage for herself or perform a marriage for someone else, regardless of whether she has attained the permission or not, even if there are ijab and qabul from the woman.
This is based on a hadith from Abu Hurairah RA, Rasullullah PBUH said:
لاَ تُزَوِّجُ الْمَرْأَةُ الْمَرْأَةَ وَلاَ تُزَوِّجُ الْمَرْأَةُ نَفْسَهَا
“A woman may not give a woman in marriage, nor may she give herself in marriage,” 
The companions R.Anhum called a woman who gives herself for marriage as an immoral woman, while in another narration she is called as an adulterer.
According to the presented question, a fasiq wali is an unjust wali. The meaning of just here is a person who does not commit a major sin or isn’t continuous in committing minor sins, doesn’t degrade himself with acts such as peeing by the road, walking without shoes and others. A fasiq wali, an unjust man is impermissible to give his daughter in marriage, rather the right as a wali is transferred to the next just wali according to the order. 
This follows the words of Ibn Abbas R.Anhuma:
لا نِكَاحَ إِلا بِوَلِيٍّ مُرْشِدٍ وَشَاهِدَيْ عَدْلٍ.
“A marriage is invalid except by a mursyid wali and two fair witnesses.” 
Imam al-Syafie said: The meaning of mursyid in the hadith is just. The reason, fasiq is a weakness that harms a testimony and prevents a wali in a marriage.
Likewise, in a hadith which is used as evidence that a wali is a valid condition for marriage is the words of the Prophet PBUH:
لَا نِكَاحَ إلَّا بِوَلِيٍّ وَلَا بِشَاهِدَي عَدْلٍ
“There is no marriage except with a wali and two witnesses.” 
In madhhab al-Imam al-Syafie and others, they are of the opinion that the denial in the hadith shows the denial of the validity of a marriage or in Arabic نفي الصحة. Thus, without the presence of a mursyid wali, it leads to the implication of an invalid marriage. 
Syeikh Wahbah al-Zuhaili stated: The reason being a wali needs careful consideration which leads to maslahat. Hence, a fasiq wali is ineligible to be a wali for a woman the same for a wali for wealth. This is the opinion in madhhab Syafi’e and Hanbali. 
In another opinion, just (fairness) is not a condition in marriage. This is due to the fact that the eligibility for a person to be a wali is determined based on the familial relationship that gives rise to love and care and wanting only good for the person under his care, regardless of whether he is just or otherwise. The reason is, placing fairness as a condition will become a huge burden, for only a few people are just, especially in this day and age. At any time, it has never been known that a fasiq is prohibited against giving his daughter for marriage. 
To close, we conclude that the marriage of a person by a fasiq wali is valid, however, we advise that one should begin the solemnization ceremony together with syahadah and istighfar. Likewise, the istighfar and repentance should be done several times before the solemnization ceremony. Furthermore, take this opportunity to advise the wali to repent and recite istighfar. The reason is in our current time, finding a person who isn’t a fasiq according to the fasiq evaluation of previous times is difficult. Thus, if the wali is wali mujbir, then one should first ask him to first repent before the solemnization ceremony or he can hand over the responsibility to the imam.