What is the ruling of Islamic law regarding a man who said to his wife: "If you do not return with me, then it is unlawful for me until you are divorced and your divorce paper reaches you," or "Upon me be the threefold divorce," and then he regretted his statement and the wife desires separation?

The phrases mentioned in the question—some depend on the husband's intention, some are a promise of divorce, and some are a conditional divorce. The majority of scholars hold that a conditional divorce takes effect if the condition is met, contrary to Ibn Taymiyyah. So, if the husband intended by his wife's return with him that she return immediately or within a period less than a week, then divorce occurs upon her not returning. And if he uttered the triple divorce, she becomes unlawful for him until she marries another husband. However, if by his oath he intended her return at any time, then no divorce occurred by her return. It is advised to refer to the Sharia court to rule on this matter. It is the wife's right to be housed by the husband in an independent dwelling, unless she willingly agrees to live with his family by her own choice. The husband must not rush into uttering words of divorce or using them in oaths.