Marriage Fiqh: Consent of Wali or Guardian is very important

Islam disapproves all those marriages which are being done without consent of Wali.

Allah swt has said in Holy Quran:

Wed them with the permission of their own folk (guardians, Auliyâ' or masters) (An-Nisa 4:25)

On another instance Allah swt says while addressing walis of women:
Arrange the marriage of the spouseless among you – [Qur'an 24:32]

Similarly there are many hadiths which highlights importance of wali.Some of them are as follows:

“Abu Musa (ra) reported that Allah’s Messenger said, ‘Marriage is not performed if (consent of the) guardian is not there.” ( Al-Tirmidhi, 1101; Abu Dawood, 2085; Ibn Maajah, 1881. Classed as saheeh by Shaykh al-Albaani in Saheeh al-Tirmidhi, 1/318)”

“Ayesha (raa) reported that Allah’s Messenger said, ‘If any woman marries without the consent of her guardian then her marriage is void. Her marriage is void. Her marriage is void. If he cohabits with her then for her is the dower as the man enjoyed her. And if her awliya disputes with each other then the ruler is the wali of the one who has no wali ” (Al-Tirmidhi, 1102; Abu Dawood, 2083; Ibn Maajah, 1879. Classed as saheeh by al-Albaani in Irwa’ al-Ghaleel, 1840)”

Saeed ibne Musayyib narrated that ‘Umar ibn al-Khattab (ra) said, ‘the woman does not get married off unless with the permission of her wali or permission of someone responsible good judgment or the sultan.’ ( Kanz ul ‘Ummal vol. 12 pg 530)

In case of virgin wali has domination on girl but in case of widowed or divorced the opinion of woman has domination on opinion of walis.

Allah says in Holy Quran about divorced women:

When they have fulfilled their term, there is no blame on you if they dispose of themselves in a just and reasonable manner. – [Qur’an 2:234]

Similarly there is hadith in sahih Muslim about previously married woman:

“Ibn Abbas (ra) reported Allah’s Messenger as saying: A previously married woman (thaib) has more right to her person than her guardian. And a virgin should also be consulted, and her silence implies her consent.”( Sahih Muslim, in Kitab-an-Nikah)