When is it permissible to declare a person a Kafir?

Q 2: When is it permissible to declare a person a Kafir (disbeliever) and when is it impermissible? What type of Kufr (disbelief) is mentioned in Allah's statement, And whosoever does not judge by what Allâh has revealed, such are the Kâfirûn (i.e. disbelievers of a lesser degree as they do not act on Allâh’s Laws). ?

A 2: You should explain to us the issues you find confusing in order to give you the ruling regarding declaring someone a disbeliever.Regarding the type of Kufr in Allah's statement, And whosoever does not judge by what Allâh has revealed, such are the Kâfirûn (i.e. disbelievers of a lesser degree as they do not act on Allâh’s Laws). It is a major disbelief. In his Tafsir (exegesis of the meanings of the Qur'an), Al-Qurtuby said that Ibn `Abbas (may Allah be pleased with them) and Mujahid (may Allah be merciful to him) said, "Whoever does not rule according to what Allah has revealed, contradicting the Qur’an and denying the statements of the Messenger of Allah (peace be upon him) is a Kafir (disbeliever)."However, if someone rules according to other than what Allah has revealed because of bribes, enmity toward the convicted, being a relative to or having ties of friendship with the plaintiff...Etc., while knowing that they are disobeying Allah, they do not commit major disbelief. They are just disobedient. (Part No. 2; Page No. 142) They commit an act of lesser Kufr, injustice, and Fisq (corruption) without deliberately being a doctrinal Kafir, unjust, or Fasiq (someone openly and flagrantly violating Islamic law; corrupt).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.