To what extent is the marriage contract valid that was concluded between the questioner's sister and a young man whom the father does not approve of, after the sister claimed she was expelled from the home, and appointed a lawyer to sign the contract, despite the father's continuous refusal and his insistence on the invalidity of the marriage without a guardian?

The majority of scholars stipulate the guardian (wali) for the validity of marriage, and a marriage without a guardian is null and void. It is not permissible for the guardian to prevent his female ward from marrying a suitable suitor. If the suitor is suitable, the father must marry his daughter to him; otherwise, he is not obliged. The sister is not allowed to marry a young man without a guardian, and her marriage is invalid, and she must separate from him. If the young man is suitable and the father refuses, she may refer her case to the Sharia judge. If he is not suitable, she must obey her father. She must fear Allah and be dutiful to her parents.