What is the ruling on someone who says about a person: "He is free to permit and forbid as he wishes," and when advised that permitting and forbidding are the right of Allah and His Messenger, he is astonished and cites the fatwas of scholars? Is this considered taking lords besides Allah, and is repentance obligatory upon him?

It is a forbidden error to say that a person has the freedom to declare something permissible (halal (definition)) or forbidden (haram (definition)); because that is a matter of legislation (tashri') which belongs exclusively to Allah Almighty alone. It is forbidden for a Muslim to declare something permissible or forbidden without a legal basis, for that involves fabricating lies against Allah Almighty and speaking about Him without knowledge, which is among the major sins. Absolute legislation is a pure right of Allah Almighty alone, and the Quranic verses explicitly affirm this.

As for the scholars, they do not declare things permissible or forbidden on their own accord; rather, they clarify legal rulings based on their derivation from the texts of revelation. It is obligatory upon the Muslim to obey Allah and His Messenger, and to accept legal rulings once the evidence becomes clear to him. Whoever follows other than Allah's ruling after knowing it has committed shirk (definition) (polytheism). So, whoever obeys other than Allah in declaring permissible what Allah has forbidden, or forbidding what He has declared permissible, has taken him as a lord and an object of worship, and this contradicts monotheism (Tawhid (definition)).