In November 2004 the Jordanian court issued a statement on what Islam is and on who may speak for it, and in July 2005 an international conference in Amman gathered scholars from across the Muslim world to endorse it. The document is known as the Amman Message, and its substance is three points.
The first recognises eight schools of Islamic law as valid: the four Sunni schools, the Ja'fari and Zaydi schools associated with Shia Islam, the Ibadi school of Oman and East Africa, and the Zahiri school, together with Ash'ari theology, the practice of Sufism and Salafi thought. The second forbids declaring any adherent of those schools an unbeliever, which is the technical act of takfir and the licence under which a great deal of violence between Muslims has been justified. The third sets conditions on who may issue a fatwa and bars anyone outside them from doing so.
None of this is enforceable. There is no body that can bind the schools it names, and the message says as much by resting on endorsement rather than on jurisdiction. What it did instead was put a very large number of senior signatures, from institutions that ordinarily do not sign the same page, against a single proposition: that mutual excommunication is out of bounds. Amman is where that signature list was assembled, and the name of the city has travelled with the document ever since.