Rabbenu Gershom's most famous ruling was his outlawing of polygamy. Professor Avraham Grossman of Hebrew University argues that he was rubber-stamping a changed social reality; by the time Rabbenu Gershom issued his ban in Mainz, Germany in 1000, most Jewish communities had no polygamy. More significant was his edict forbidding a man to divorce a woman against her will, which according to Grossman, marked great progress in the status of women in Jewish law.
Yemenite Jews never accepted Rabbeinu Gershom's ban and until this day practise polygamy in Yemen. In Israel it is forbidden by law. A fringe group in Israel recently ran an ad in a popular Sephardic Shabbat newsletter calling for men to be allowed more than one wife. They pointed to the Bible as the ideal model. However, all the biblical cases of polygamy are wracked with anguish and competitiveness, from Abraham, Sarah and Hagar to David and the sons of his many wives. The Torah would seem to be telling us that polygamy was a disastrous family model.