The concept of guardianship (wilayah) is particularly important in Twelver Shii political theory, where it signifies the legitimacy of Ali's claim, together with that of the successor imams, to lead the Islamic community. In Islamic law, the term refers to guardianship of minors. For minors or the mentally ill, the father serves as legal guardian in most systems of Islamic law. In Maliki, Hanbali, and Shafii Islamic law, a guardian has the legal authority to contract marriage on behalf of a previously unmarried Muslim woman. Hanafis and the Shii Jafaris permit the interference of a guardian only if the bride's dowry is insufficient or in the event she wishes to marry someone who is not her equal according to law.