What is the ruling on the marriage of an adulterer to the woman with whom he committed adultery, and is she entitled to marry herself in the event that her guardian refuses for unconvincing reasons?

Adultery is a grave sin that Allah has forbidden and for which He has threatened its perpetrators with punishment, except for those who repent, believe, and do righteous deeds. If the adulterer and adulteress repent, it is permissible for them to marry, as narrated by Ibn Majah: "The one who repents from a sin is like one who has no sin." Abu Bakr Al-Siddiq married two adulterers after they had been punished, and Ibn Abbas said: "Its beginning is fornication, and its end is marriage." As for a woman marrying herself off, it is not valid.