What is the ruling regarding a husband's statement to his wife: "You are unlawful to me until your family comes," knowing that her family is in one country while the wife is in another, and what is the expiation for that?

Prohibiting one's wife refers back to the husband's intention. If he intended divorce, then there is a detailed explanation: did the husband intend a conditional divorce or not? If he intended zihar, it becomes a temporary zihar, and he must offer kaffarat az-zihar (expiation for zihar) if he wishes to enjoy her before her family returns. If he intended a conditional zihar, it does not occur unless the condition is met. If he intended an oath, he must offer kaffarat al-yamin (expiation for breaking an oath) if he breaks it.