What is the ruling on a man marrying a Christian woman without a guardian (wali) or witnesses, with the absence of witnesses being compensated by public announcement? Is this marriage considered void and tantamount to fornication?

For a marriage to be valid, the presence of a guardian (wali) and two just witnesses is required, based on the Prophet's (peace be upon him) sayings: "There is no marriage without a guardian," and "Any woman who marries without the permission of her guardian, her marriage is invalid," and "There is no marriage except with a guardian and two just witnesses." If the father refuses to marry off his daughter to a Muslim, the guardianship transfers to the next in line. If all of them refuse, the head of the Islamic Center or the Imam of the mosque should marry her off. Scholars have concluded that a marriage contracted without a guardian or two witnesses is invalid, and the contract must be renewed with its Sharia-compliant conditions.