Question: What is the Islaamic ruling regarding (Ayatollah) Khomeini?

Response: Khomeini has a book in which he mentions the excellence of the Imaams (Hassan and Hussein et al) of the family of the Prophet (sal-Allaahu `alayhe wa sallam) over and above the Prophets and the Messengers (`alayhim as-salaam); (So) based upon this (statement of his) he is not a Muslim.

Shaykh al-Albaanee
al-Haawee min Fataawa ash-Shaykh al-Albaanee – Page 349

source: www.fatwa-online.com

Based on this, we can see that it is Kufr (disbelief) to say that there exists anyone superior to the Prophets and Messengers, such as the Shia say of their Infallible Imams. It is therefore the ruling of the scholars that such a person is not a Muslim and outside the folds of Islaam.