Ruling on Calling an alcoholic Muslim a Kaafir

Question 387: Is it permissible for a Muslim to call another Muslim who drinks Khamr (intoxicant) a Kaafir (disbeliever)?

Answer: Drinking Khamr, committing Zinaa (fornication or adultery) and withholding one’s Zakaah (obligatory charity) are major sins that may be forgiven only through repenting to Allaah (Glorified and Exalted be He). According to Ahl-ul-Sunnah wal-Jamaa`ah (those adhering to the Sunnah and the Muslim community) anyone who commits a major sin is considered a believer by virtue of his Eemaan (Faith), but his major sin renders him a Fasiq (someone openly and flagrantly violating Islaamic law). Therefore, it is not permissible to call this sinner a Kaafir as long as he does not deem his sinful act lawful, or is satisfied with it... read more here.