Can a caliph become one without a bayah, i.e. through power or coercion?

In a Nutshell: A caliph can be bought to power by force given certain conditions are met. Taghalub (coercion) is one of the ways of establishing a caliph out of necessity i.e., to spare the blood of Muslims. The following conditions however must be fulfilled: - the mutaghalib (the one who wants to take the power) must be a Muslim; - there is no legally appointed ruler who was not mutaghalib; - the power of mutaghalib has to be overwhelming; - the mutaghalib must rule the Muslims with the shari'ah of Allah. If the mutaghalib killed or imprisoned the previously legally appointed ruler who cannot be rescued, the influentials (ahl al-hal wa al-aqd) have to appoint a new caliph. Introduction This question often arises when reviewing Islamic history where some individuals became caliphs by force, or in contemporary times where individuals take power by force and there is no bayah. Classical scholars were unanimous that a bayah was always required for legitimacy and it would historically always be given. It is the contract between the people and the ruler, legally transmitting the divine authority invested in them by Allah to implement his laws across society. The classical jurists identified three main ways for imam or a caliph to be legally valid and his rule to be legally binding: the election of the people of legal influence (Ahl al-Hil wa al-Aqd), such as the way of electing Abu Bakr, Uthman and Ali (ra); through the will (wisayah) of the previous caliph appointing another recommended caliph/s after him, such as the way of electing Umar (ra) as a caliph by the will of the recommendation of Abu Bakr (ra) before he passed away; or al-ghalabah (coercion) of a person over another ruler. (Mawardi, al-Ahkam al-Sultaniyyah, Dusuqi, al-Hashiyah ala Sharh al-Kabir, Vol. 4, p. 298) In this answer, I will only focus on the third way of establishing a caliph: its legal status and conditions. Misconceptions Some contemporary Muslim movements (such as the Jamiyyah and Madakhilah) support contemporary rulers who reached power by coercion, arguing they are now mutaghalib rules who must be obeyed and it is prohibited to oppose them. So, they misunderstood, or distorted, the notion presented in the classical scholarship which applies to Islamic polities, not secular nation states, thereby causing confusion and discord amongst the Muslim masses. Evidences Qur'an: وَلَنْ يَجْعَلَ اللَّهُ لِلْكَافِرِينَ عَلَى الْمُؤْمِنِينَ سَبِيلًا "Never will Allah give the disbelievers over the believers a way (of authority)." (Qur'an 4:141) Sunnah: مَنْ أَتَاكُمْ وَأَمْرُكُمْ جَمِيعٌ عَلَى رَجُلٍ وَاحِدٍ يُرِيدُ أَنْ يَشُقَّ عَصَاكُمْ أَوْ يُفَرِّقَ جَمَاعَتَكُمْ فَاقْتُلُوهُ "When you are holding to one single man as your leader, you should kill who seeks to undermine your solidarity or disrupt your unity." (Muslim, 4567) إِنْ أُمِّرَ عَلَيْكُمْ عَبْدٌ مُجَدَّعٌ ...  أَسْوَدُ يَقُودُكُمْ بِكِتَابِ اللَّهِ فَاسْمَعُوا لَهُ وَأَطِيعُوا "If a maimed slave is appointed a commander over you … who leads you according to the Book of Allah, then listen to him and obey him." (Sahih al-Muslim 4532) Sahabah: Ibn Umar (ra) said: نَحْنُ مَعَ مَنْ غَلَبَ "We are with whoever takes over." (Abu Ya'la, al-Ahkam al-Sultaniyyah, p. 24) Juristic Views Classical scholars agree that the legal status of a caliphate built on coercion becomes a necessity Muslims have to collectively seek to remove. However, they stipulate a number of conditions to accept this procedure as legally valid (even if sinful and undertaken out of necessity) and any violation of these conditions will not be considered as a legally valid caliphate or rule. Taghalub's Legal Status The first two ways are acceptable by all classical scholars as a legally binding way of establishing a caliph, but the third way was considered legally acceptable, subject to fulfilling the conditions below, out of necessity and Muslims should seek its abolishment when possible so long it does not lead to severe problems. For example, Imam Malik, the founder of the Maliki madhab, gave a fatwa to rebellion against a contemporary ruler who took the power and bay'ah by force. (Dhahabi, Tarikh al-Islam, Vol. 4, p. 729) He justified his fatwa saying: مِنْ بُويِعَ لَهُمْ عَلَى الْخَوْفِ لَا بَيْعَةَ لَهُم "Whoever receives the bay'ah out of fear, there is no (binding) bay'ah for them." (Ibn al-Arabi, Ahkam al-Qur'an, Vol. 4, p. 154) Similarly narrated Abu Hanifah who used to secretly urge people to fight with Zayd ibn Ali against a mutaghalib ruler (one who took power by coercion) 'Dawaniqi.' (Qununi, Hashiyah, Vol 4, p. 212) It was also followed by later jurists and theologians, such as Ibn Hajar al-Haytami (al-Sawa'iq, Vol. 2, p. 627) and Imam Juwayni (Ghiyath al-Umam, p. 327). All classical jurists justify allowing the rule of mutaghalib out of necessity preventing shedding the blood of great number of Muslims. Ibn Batal narrated this justification: لِمَّا فى ذَلِكَ مِنْ حَقْنِ الدِّماءِ وَتَسْكِينِ الدَهْماءَ "Because of sparing the blood (of Muslims) and calming the multitude." (Ibn Batal, Sharh Sahih al-Bukhari, Vol. 10, p. 8) Haskafi, the tenth-century Hanafi jurist, also argued: وَتَصِحُّ سَلْطَنَةَ مُتَغَلِّبٍ لِلضَّرُورَةٍِ "The rule of mutaghalib is legally valid for necessity." (Ibn Abidin, Rad al-Muhtar, Vol. 1, p. 549) This necessity (darurah) has to be removed when possible, making it similar to the necessity of eating pork or drinking alcohol in times of no water or food. (Muhammad Rashid Rida, al-Khilafah, p. 45) Conditions for accepted Coercion When the taghalub is considered a necessity, classical jurists identify a number of conditions for this necessity to be legally valid: 1. There is a consensus of classical jurists that the mutaghalib ruler must be a Muslim, as Allah says:  'Never will Allah give the disbelievers over the believers a way (of authority)' (Qur'an 4:141) Qadi Iyad and other narrated the ijma on this: لَا خِلاَفَ بَيْنَ الْمُسْلِمِينَ أَنَّه لَا تَنْعَقِدُ الْإمَامَةَ لِلْكَافِرِ "The is no dispute between Muslims on the notion of 'it is not valid to appoint a kafir as an imam.'" (Qadi Iyad, Sharh Muslim, Vol. 6, p. 246) The same was argued by ibn Hazm (Maratib al-Ijma, Vol. 1, p. 126), Abu Ya'ala (Al-Mu'tamad fi al-Usul, p. 243), ibn Al-Teen (Irshad al-Sari, Vol. 10, p. 209), and others. 2. There must be no legally appointed ruler who was not Mutaghalib i.e. a ruler appointed by the first two ways of establishing the caliph. So, if a man comes and wants to take the power over a previously legally elected caliph, it would not be considered an approved taghalub, rather a rebellion that has to be stopped. On the other hand, if he came over a previous mutaghalib, his taghalub would be legally approved. (Qiliqshandi, Ma'athir al-Inafah, Vol. 1, p. 30, Ibn al-Humam, al-Musayarah fi al-Aqa'id, p. 274, Shirwani, Hawashi, Vol. 9, p. 78, Nawawi, Rawdat al-Talibin, Vol. 10, pp. 46-48, Mas'udi, al-Bayan, Vol. 12, p. 14, Ibn al-Mundhir, al-Ishraf, Vol. 8, p. 238, Umrani, al-Intisar fi al-Rad ala al-Mu'tazilah, Vol. 3, p. 823) The tenth-century Shafi'i jurist al-Khatib al-Shirbini noted: أَمَّا الْاِسْتيلاءُ عَلَى الْحَيِّ فَإِن كَانَ الْحَيُّ متغلبًا اُنْعُقِدْت إمَامَة الْمُتَغَلَّب عَلَيه، وَإِنَّ كَانَ إمَامًا بِبَيْعَةٍ أَوْ عَهْدٍ لَمْ تَنْعَقِدْ إمَامَةَ الْمُتَغَلَّب عَلَيه "For taking over a living (caliph): if the living ruler was a mutaghalib, the rule of the one who overcame him is considered valid. But if he was an imam due to a bay'ah or ahd (will), the rule of the mutaghalib is not legally binding." (Shirbini, Mughni al-Muhtaj, Vol. 5, p. 423)  The evidence of this comes from the hadith: مَنْ أَتَاكُمْ وَأَمْرُكُمْ جَمِيعٌ عَلَى رَجُلٍ وَاحِدٍ يُرِيدُ أَنْ يَشُقَّ عَصَاكُمْ أَوْ يُفَرِّقَ جَمَاعَتَكُمْ فَاقْتُلُوهُ "When you are holding to one single man as your leader, you should kill who seeks to undermine your solidarity or disrupt your unity." (Muslim, 4567) In another narration:  فَاضْرِبُوهُ بِالسَّيْفِ كَائِنًا مَنْ كَانَ "Strike him with the sword, whoever he be." (Abu Dawud 4762) So, he has to be fought even if this leads to killing the transgressor. (Nawawi, Sharh Muslim, Vol. 6, p. 202) Marginal issue: If the person who seeks to overcome the legally elected caliph murdered or imprisoned him, the influentials (ahl al-hal wa al-Aqd) have to appoint a new caliph to oppose the transgressor and to rule the life of Muslims. (Nifarawi, al-Fawakih al-Dawani, Vol. 1, p. 107, Juwayni, Ghiyath p. 116, Nawawi, Rawdat, Vol. 10, p. 49, Qilqashandi, Vol. 1, pp. 70-71) Mawardi noted: وَلِلْأُمَّةِ اِخْتِيَارُ مِنْ عَدَاه مِنْ ذَوِيَ الْقُدْرَةِ، وَإِنَّ أُسِرَ بَعْدَ أَنْ عُقَدْتِ لَهُ الْإمَامَةُ فَعَلَى كَافَّةِ الْأُمَّةِ اِسْتِنْقاذَهُ لَمَّا أَوُجِبْتْه الْإمَامَةَ مِنْ نُصْرَتِهِ وَهُوَ عَلَى إمَامَتِهِ مَا كَانَ مَرْجُوُّ الْخلاصِ مَأْمُولُ الْفِكَاكِ إِمَّا بِقِتَالٍ أَوْ فَدَاءٍ، فَإِنَّ وَقْعً الإياس مِنْه … فَعَلَى أهْلِ الْاِخْتِيَارِ فِي دَارِ الْعَدْلِ أَنْ يَعْقِدُوا الْإمَامَةَ لَمِنْ اِرْتَضَوْا لَهَا "The Ummah has to elect other than him from the people of capability. If he (the ruler) was arrested after the rule was given to him, all the Ummah collectively has to rescue him according to what the (bay'ah for) ruling necessitate to him. This is in a case if he was rescuable by fighting or ransom. But if they could not release him … people of electing (Ahl al-Hal wa al-Aqd) have to establish the caliphate of whoever they are satisfied with." (Mawardi, al-Ahkam al-Sultaniyyah, p. 47-48) 3. The power of mutaghalib has to be overwhelming among people and all have surrendered to him. So, he has to have a social and political basis for his taghalub. For example, when ibn al-Zubayr was struggling with Abd al-Malik ibn Marwan over the caliphate, Ibn Umar (ra) said: "We are with whoever takes over." (Abu Ya'la, al-Ahkam al-Sultaniyyah, p. 24) Abu al-Hasan al-Ash'ari, the founder of Ash'ari theological school, noted the condition: وَاُمْتُدَّتْ طَاعَتُهُ مِنْ بَرِّ وَفَاجِرِ "Obedience to him was stretched (and was followed) by the good and the bad." (Abu al-Hasan, Risalah ila Ahl al-Thaghr, p. 296) The same condition was stipulated by Ibn Batal (Sharh al-Bukhari, Vol. 2, p. 328), Ibn Qudamah (al-Mughni, Vol. 9, p. 5) and others. 4. The Mutaghalib must rule the Muslims with the shari'ah of Allah (swt) and if he seeks to apply the contrary to the shari'ah, his taghalub would not be legally approved. (Qastalani, Irshad al-Sari, Vol. 1, p. 169) For example, Mawardi argued: وَإِن كَانَتْ أَفْعَالُهُ خَارِجَة عَنْ حُكْمِ الدَّيْنِ وَمُقْتَضى الْعَدْلِ لَمْ يَجُزْ إقْرَارُهُ عَلَيهَا وَلَزِمَهُ يُسْتَنْصَرُ مَنْ يَقْبِضُ يَدَهُ وَيُزِيلُ تَغَلُّبَهُ. "If his acts are contrary to the rulings of the deen and justice, it is not legally allowed to approved his (taghalub) and (Muslims) has to seek help from who can prevent him and remove his taghalub." (Mawardi, al-Ahkam al-Sultaniyyah, p. 47) Ibn Abidin also noted this condition: إِذَا لَمْ يُخَالَفْ الشَّرْعُ "Providing he is not opposing the shari'ah." (Ibn Abidin, Rad al-Muhtar, Vol. 4, p. 263) They cite the hadith of the Prophet (saw) stipulating the same condition for taghalub to be legally approved: إِنْ أُمِّرَ عَلَيْكُمْ عَبْدٌ مُجَدَّعٌ ...  أَسْوَدُ يَقُودُكُمْ بِكِتَابِ اللَّهِ فَاسْمَعُوا لَهُ وَأَطِيعُواا "If a maimed slave is appointed a commander over you … who leads you according to the Book of Allah, then listen to him and obey him." (Sahih al-Muslim 4532) Analysis We could deduce from the above juristic analysis that most (or none) of our contemporary rulers fulfils these conditions in order to call him a mutaghalib ruler. One of the early historical examples of a taghalub fulfilling the above conditions was Abd al-Malik ibn Marwan who was fighting with Ali ibn al-Zubayr, who took the bay'ah by force. For that reason, contemporary jurists, such as imam Malik, gave fatwa to obey and listen to him. (Ibn Qudamah, al-Mughni, Vol. 8, p. 527, Shatibi, al-I'tisam, Vol. 2, p. 182) Conclusion The taghalub (coercion) is one of the ways of establishing a caliph out of necessity for sparing the blood of Muslims. But the following conditions must be fulfilled: The Mutaghalib must be a Muslim; There is no legally appointed ruler who was not Mutaghalib; The power of mutaghalib has to be overwhelming among all types of people; The Mutaghalib must rule the Muslims with the shari'ah of Allah. 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