Back in 2004, King Abdullah II of Jordan sent three deceptively simple questions to 24 religious scholars representing major trends of thought within Islam: (i) Who is a Muslim?; (ii) Is it permissible to declare another Muslim an apostate?; and (iii) Who has the right to issue non-binding legal verdicts ( fatawa)? The immediate context was not only al-Qaeda-type terrorism, but the emerging sectarian conflict in Iraq; however, it should also be recognised that the questions touched too on fundamental issues about the nature of orthodoxy, its self-definition and self-regulation. Their answers, subsequently endorsed by over 500 leading religious scholars in a series of six major conferences, affirmed that there were eight orthodox legal schools, that no-one had the right to declare anyone an apostate on this broad definition, and that all these legal schools had collectively developed substantive criteria upon which a fatwa could be authoritatively issued (and thus the issuing of fatawa could not be the provenance of ignoramuses, fanatics or overweening autodidacts).
Named after the first major conference, held in July 2005, these "three principles of the Amman message" form the basis of global Muslim unity, the grounds for the advancement of peaceful Muslim relations, and an endorsement of the means by which religious scholarship moderates extremism in matters of religious interpretation.
(1) Whosoever is an adherent to one of the four Sunni schools (Madhahib) of Islamic jurisprudence (Hanafi, Maliki, Shafi`i and Hanbali), the two Shi’i schools of Islamic jurisprudence (Ja`fari and Zaydi), the Ibadi school of Islamic jurisprudence and the Zahiri school of Islamic jurisprudence, is a Muslim. Declaring that person an apostate is impossible and impermissible. Verily his (or her) blood, honour, and property are inviolable. Moreover, in accordance with the Shaykh Al-Azhar’s fatwa, it is neither possible nor permissible to declare whosoever subscribes to the Ash`ari creed or whoever practices real Tasawwuf (Sufism) an apostate. Likewise, it is neither possible nor permissible to declare whosoever subscribes to true Salafi thought an apostate.
Equally, it is neither possible nor permissible to declare as apostates any other group of Muslims who believes in God, Glorified and Exalted be He, and His Messenger (may peace and blessings be upon him), the pillars of faith ( Iman), and the five pillars of Islam, and does not deny any necessarily self-evident tenet of religion.
(2) There exists more in common between the various schools of Islamic jurisprudence than there is difference between them. The adherents to the eight schools of Islamic jurisprudence are in agreement as regards the basic principles of Islam. All believe in Allah (God), Glorified and Exalted be He, the One and the Unique; that the Noble Qur’an is the Revealed Word of God preserved and protected by God, Exalted be He, from any change or aberration; and that our master Muhammad, may blessings and peace be upon him, is a Prophet and Messenger unto all mankind. All are in agreement about the five pillars of Islam: the two testaments of faith ( shahadatayn); the ritual prayer (salat); almsgiving (zakat); fasting the month of Ramadan (sawm), and the Hajj to the sacred house of God (in Mecca). All are also in agreement about the foundations of belief: belief in Allah (God), His angels, His scriptures, His messengers, and in the Day of Judgment, in Divine Providence in good and in evil. Disagreements between the ‘ulama (scholars) of the eight schools of Islamic jurisprudence are only with respect to the ancillary branches of religion (furu`) and some fundamentals ( usul) [of the religion of Islam]. Disagreement with respect to the ancillary branches of religion ( furu`) is a mercy. Long ago it was said that variance in opinion among the ‘ulama (scholars) "is a mercy".
(3) Acknowledgement of the schools of Islamic jurisprudence (Madhahib) within Islam means adhering to a fundamental methodology in the issuance of fatwas: no one may issue a fatwa without the requisite qualifications of knowledge. No one may issue a fatwa without adhering to the methodology of the schools of Islamic jurisprudence. No one may claim to do unlimited Ijtihad and create a new opinion or issue unacceptable fatwas that take Muslims out of the principles and certainties of the Shari`ah and what has been established in respect of its schools of jurisprudence. 
It should be noted that it was not only representatives of the eight schools — Hanafi, Maliki, Shafi`i, Hanbali, Ja`fari, Zahiri, Ibadi and Zaydi — who endorsed this declaration, but, according to one eyewitness account, it was even more inclusive than that:
It was significant that in addition to Iraqi and Iranian mainstream Shi’a scholars, representatives of the smaller Shi’a currents—the Isma’ili followers of the Aga Khan and the Bohra Isma’ilis, as well as the Shi’a Zaydis of north Yemen, signed off on this document. 
This terribly important reaffirmation, in times of Muslim political fragmentation, "fraternal" bloodshed and disintegrating religious authority, has now emerged from the counsels of the good and the great to be presented to everyone. The entire Amman Message can be read in full here The Amman Message . They are now asking everyone who agrees with this restatement of inclusive orthodoxy to sign up online and endorse it Invitation to Endorse the Amman Message . Major religious and political Muslim leaders of Europe and North America have already endorsed these three principles, in Istanbul in July 2006, alongside a commitment to respect fundamental rights and freedoms and to contribute to the welfare and good of those societies of which they are citizens. 
There is now also an effort Amman Message underway to spread the ethos of these three foundational principles further, which should be supported, through these mooted practical measures:
(1) inter-Islamic treaties;
(2) national and international legislation using the Three Points of the Amman Message to define Islam and forbid takfir;
(3) the use of publishing and the multi-media in all their aspects to spread the Amman Message;
(4) instituting the teaching of the Amman Message in school curricula and university courses worldwide; and
(5) making it part of the training of mosque Imams and … [including it] in their sermons.
Of course, it could be pointed out that such declarations are only made when religious orthodoxy no longer holds the centrality it once had, and that, with this marginalisation, some foundational values, such as upholding the inviolability of the faith, life, honour and property of Muslims, are fraying within the umma-politic. Bin Laden affirmed in one his messages that the 9/11 attacks were conducted without reference to any recognised school of fiqh, and so the problem is not that al-Qaeda is unorthodox but that it refuses to recognise orthodoxy in the first place. 
The Islamo-anarchists will no doubt ignore all " fatwas of peace" issued by well-intentioned international conferences and platforms. But they are not the principal audience for this reaffirmation; rather, it is the umma at large. Given the wide assent for these three principles, this can be held, for all practical purposes, to constitute a consensus of the umma, and as such, some have argued that affirming them becomes an individual legal, and not just a moral, obligation ( fard `ayn).
Even for those who are reluctant to be seen to endorse a conception of orthodoxy, and hence the age-old role and status of traditional religious scholarship within Islam, ought at least to recognise the basic impetus behind these three principles, which is to reassert basic civilised religious norms in a genuinely inclusive spirit. The declaration is not a panacea for the fragmentation of religious authority in the House of Islam, because the structural issues underlying that process are not going away but are in fact intensifying. Rather, signing up for it is the very least that one can do to avoid a Muslim equivalent of Europe’s early modern "wars of religion", which appears, at the current juncture, to be a distinct and disastrous possibility.
 The second version of the three principles endorsed at the Islamic Fiqh Academy of the Organisation of the Islamic Conference in June 2006; the first version, which was substantially the same, was endorsed in Amman in July 2005. The second version is available online here: Link.
 Abdullah Schleifer, "The Amman Initiative: A Theological Counter-Attack against Terrorism", Islamica Magazine, 14, 2005, avaiable at: Link.
 Topkapi Declaration, July 2006, available at: Link.
 Faisal Devji, Landscapes of the Jihad (London: Hurst, 2005), 13.