Is the marriage of a Muslim man to a Muslim woman who has no guardian valid, with her saying: "I marry myself to you," and his saying: "I accept to marry you," and what is the ruling on their relationship?

A marriage contracted without a guardian (wali) or witnesses is invalid, and it is impermissible for you to have conjugal relations with her. If both of you desire to continue the marriage, the marriage contract must be performed in its legally prescribed manner. If the wife does not have a Muslim guardian to marry her off, a Shariah judge can act in his stead. If no such judge is available, she should appoint an upright Muslim man. It is incumbent upon anyone ignorant of a religious ruling to ask people of knowledge before undertaking an action. Allah the Almighty says: "So ask the people of the message if you do not know."