Fadlallah of Lebanon provides a ruling on who may be considered a Muslim

Religious Authority: 
Sayyad Muhammad Hussein Fadallah
Fatwa Question or Essay Title: 
Is it permissible to consider as a Muslim any person who believes that there is not God but God and Muhammad is his prophet and follows one of the eight Islamic schools ( Maliki, Shafii, Hanbali, Hanafi, Jafari, Zaydi, Ibadyya, and Aldhahirya)? And what is the ruling on declaring one of the followers of these schools an apostate?
Websites and Institutions: 
Amman Message, (Jordan)

[See glossary for an explication of terms.]

Answer: Anyone who believes that there is no God but God and Muhammad is his prophet is a Muslim. He has the same rights and duties that any Muslim has.

Therefore, it is not permissible to declare any one who is part of one of these groups or sects an apostate. Even denying one of the requirements of Islam except denying the prophet does not give the right to declare a Muslim an apostate. So all these groups and sects are part of the Islamic nation and should resolve the problems and discuss differences with substantive dialogue

[Note: For similar opinions, search: Amman Message.]