The criteria by which the permissibility of a forbidden act is established

Question:
Fourth section: What are the criteria that a student of knowledge should know in order to rule that a certain person considers a sin, whose prohibition is unanimously agreed upon, to be permissible, such that the one who considers this sin permissible is declared a disbeliever?

Answer:
The criteria indicating that a person considers a sin permissible are that the person explicitly states that it is lawful. This is either by his tongue, or by his pen, where he writes that it is lawful, or he says that it is lawful. In that case, he is ruled to be one who considers it permissible. Without that, he is not ruled to consider it permissible until it is established against him either by speech, where he explicitly states it with his tongue, or by writing, or by two or more just Muslim witnesses testifying that he says fornication is lawful, or intoxicants are lawful, or riba (usury or interest) is lawful, or the like. In that case, he is ruled to consider it permissible, either by his verbal or written admission, or by testimony against him. Yes.