Contrary to the theory of some who limit the ruler's occupation of family rights to the necessary cases such as the administration of the affairs of the absentee or the children who do not have a specific guardian, the scope of authority of the Islamic government goes beyond the necessary matters and expands according to expediency. According to this theory, the government can provide the general interests of the Islamic society. This article has tried to explain the criteria of expediency in the Islamic government and explain its criteria in family law. The investigations of this research show that family, public, religious, religious and governmental interests are important criteria of expediency in family legal engineering. Also, in the current research, examples of expedient interventions of the government in family rights, based on the mentioned criteria, have been determined
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