What is the religious ruling regarding the marriage of a woman who left her husband's home and married another man without obtaining a divorce from her first husband, who is still devoted to her after twenty years?

A wife's escape from her husband's home without a legitimate Shar'i excuse is a forbidden act of disobedience (nushuz), and whoever assists her in it is a partner in sin. A second marriage is invalid as long as the wife is still lawfully married to her first husband. If she enters into this invalid marriage knowingly, she is an adulteress deserving of punishment, as is the man who marries her if he knows her situation. It is advised to refer the matter to the Shar'i courts.