Reference: Silsilah Kitaab ad-Da ‘wah (11), al-Fataawa – Volume 4, Page 3
Question: Does everyone who commits ash-Shirk al-Akbar (the association of a partner in worship with Allaah on a major level) become a mushrik, and thereby the [appropriate] rulings pertaining to the mushrikeen are applied upon them?
Response: Yes. Whoever disbelieves in Allaah becomes a disbeliever, and whoever commits shirk with Allaah becomes a mushrik; Just as whoever believes in Allaah and His Messenger becomes a believer (mu.min) and muwahhid (one who attests to the Oneness of Allaah).
As for he to whom the [Islaamic] da’wah has not been conveyed, then it is not said of him that he is neither a believer and nor a disbeliever, and he is not to be dealt with as a Muslim, rather his affair is with Allaah on the Day of Resurrection, and they are those who are unaware since the [Islaamic] da’wah has not been conveyed to them, they shall (instead) be tested on the Day of Resurrection.
As for him to whom the [Islaamic] da’wah has been conveyed and he has [subsequently] not believed and become a Muslim, then he is a disbeliever and an enemy of Allaah.