Does falling into forbidden acts, believing them to be out of necessity or an exception, constitute making the forbidden permissible, thereby leading one out of the faith?

The place of excommunication for deeming sins permissible is when the prohibited act is unanimously agreed upon as forbidden with definitive consensus, and its ruling is clear among Muslims. The reason for excommunication in this case is that deeming the prohibited permissible involves denying the Sharia and rejecting its ruling. A condition for excommunication is the absence of any doubt. If doubt exists, the person is not excommunicated.

Ibn Qudamah said: "Whoever believes that something is permissible, despite it being unanimously agreed upon as forbidden, its ruling being clear among Muslims, and all doubt about it having been removed due to the texts mentioning it, such as pork, adultery, and similar matters about which there is no disagreement, has committed an act of disbelief." He added that whoever deems a forbidden act permissible due to an interpretation, like the Kharijites, or out of ignorance, is not excommunicated until they are informed and the doubt is removed from them.

Ibn Taymiyyah said: "If a man denies it out of ignorance or interpretation, he is not excommunicated until the proof is established against him, just as a group of people, including Qudamah, deemed the consumption of alcohol permissible during the era of Umar, believing it to be lawful for them; and the Companions did not excommunicate them until they clarified their error, whereupon they repented and recanted."

Among the doubts that prevent excommunication is a person's belief that certain situations fall under necessity, which permits the forbidden, when in fact they do not.