Aisha (may Allah be pleased with her) narrates from the Prophet (ﷺ) that he said: "Any woman who marries without the permission of her guardian, her marriage is invalid. If the man has intercourse with her, he must pay the dowry, because he has made her private parts lawful in exchange for it. If the guardians disagree among themselves, then the ruler is the guardian of the one who has no guardian."
Hadith Referenceمسند الإمام الشافعي / كتاب النكاح / 1140