How can a Tunisian Muslim man legally marry a Russian woman who has converted to Islam, given her father's consent but his inability to be present?

For a valid Islamic marriage, the presence of a guardian (wali) is a prerequisite. The guardian of a Muslim woman must be Muslim. If the girl's father is Muslim, he is her guardian. If he is not Muslim, he has no guardianship over her, and the responsibility shifts to the next in line among her Muslim guardians. If there is no Muslim guardian available, the Sharia (definition) judge performs the marriage. If the judge is unavailable, the woman may appoint a Muslim to perform her marriage. A guardian who is not present may delegate someone to perform her marriage in her place of residence. It is advisable to seek counsel and perform Istikhara (prayer for guidance) before marriage.