This is another article in the chapter Justice from the classical manual on Sharia called Reliance of the Traveller. The articles are posted one by one in the order they are given in the book.
THE QUALIFICATIONS OF A CALIPH
025.3 (Nawawi:) Among the qualifications of the caliph are that he be:
(a) Muslim (H: so that he may see to the best interests of Islam and the Muslims (K: it being invalid to appoint a non-Muslim (kafir) to authority even to rule non-Muslims.) (S: Qadi ‘lyad states that there is scholarly consensus (def: b7) that it is not legally valid to invest a non-Muslim as caliph. and that if a caliph becomes a non-Muslim (dis: 08.7) he is no longer caliph, as also when he does not maintain the prescribed prayers (A: meaning to both perform them himself and order Muslims to) and summon the people to them, and likewise (according to the majority of scholars) if he makes reprehensible innovations (bid’a, def: w29.3) (A: by imposing an innovation on people that is offensive or unlawful). If the caliph becomes a non-Muslim, alters the Sacred Law (N: such alteration being of two types, one of which consists of his changing the Law by legislating something which contravenes it while believing in the validity of the provisions of the Sacred Law, this being an injustice that does not permit rebellion against him, while the other consists of imposing rules that contravene the provisions of the religion while believing in the validity of the rules he has imposed, this being unbelief (kufr) (A: it is questionable whether anyone would impose such rules without believing in their validity)) or imposes reprehensible innovations while in office, then he loses his authority and need no longer be obeyed, and it is obligatory for Muslims to rise against him if possible, remove him from office, and install an upright leader in his place. If only some are able, they are obliged to rise up and remove the unbeliever (A: whether they believe they will succeed or fail), though it is not obligatory to try to remove a leader who imposes reprehensible innovations unless they believe it possible. If they are certain that they are unable to (A: remove an innovator), they are not obliged to rise against him. Rather, a Muslim in such a case should emigrate from his country (N: if he can find a better one), fleeing with his religion (A: which is obligatory if he is prevented in his home country from openly performing acts of worship»);
(b) possessed of legal responsibility (def: cS.l) (K: so as to command the people, it being invalid for a child or insane person to lead);
(c) free (K: so that others may consider him competent and worthy of respect);
(d) male (K: to be able to devote himself fulltime to the task, and to mix with men, the leadership of a woman being invalid because of the rigorously authenticated (sahih) hadith,
“A people that leaves its leadership to a woman will never succeed”);
(e) of the Quraysh tribe (K: because of the (H: well-authenticated (hasan)) hadith related by Nasa’i,
“The Imams are of the Qura ysh, a hadith adhered to by the Companions of the Prophet (Allah bless him and give him peace) and those after them, this qualification being obligatory when there is a member of Quraysh available who meets the other conditions) (H: though when there is not, then the next most eligible is a qualified member of the Kinana tribe, then of the Arabs, then of the non-Arabs);
(f) capable of expert legal reasoning (ijtihad) (H: as a judge must be (def: 022.1(d)) and with even greater need (K: so as to know the rulings of Sacred Law, teach people, and not need to seek the legal opinion of others concerning uprecedented events), scholarly consensus (def: b7) having been related concerning this condition, which is not contradicted by the statement of the Qadi (A: ‘Iyad) that “an ignorant upright person is fitter than a knowledgeable corrupt one,” since the former would be able to refer matters requiring expert legal reasoning to qualified scholars, and moreover the remark applies to when the available leaders are not capable of legal reasoning (S: while possessing the other qualifications for leadership»;
(g) courageous (K: meaning undaunted by danger, that he may stand alone, direct troops, and vanquish foes);
(h) possessed of discernment (H: in order to lead followers and see to their best interests, religious or this-worldly, discernment meaning at minimum to know the various capacities of·people), sound hearing and eyesight, and the faculty of speech (K: so as to decisively arbitrate matters);
(i) (H: and be upright (def: 024.4) as a judge must be, and with even greater need. But it is valid, if forced to, to resort to the leadership of a corrupt person, which is why Ibn ‘Abd ai-Salam says, “If there are no upright leaders or rulers available, then the least corrupt is given precedence”).