In Islamic law, knowledge of haram as a judgement (hukm) category is as important as determining the deeds that are haram. Accordingly, work on usul al-fiqh describes the concept of haram from several perspectives. Pursuant to some classical Hanafi work on usul al-fiqh and certain modern usul studies, the common Hanafi view is that proof for prohibition must be definitive to determine what is haram and its denier is subjected to excommunication (takfir). Nevertheless, based on a general approach in classical Hanafi work on usul al-fiqh and the use of the.aram concept in furu' books, it is impossible to accept the foregoing view as the absolute or preferable opinion in the Hanafi school. This study discusses the correctness of this relation for the foregoing approach to the Hanafi school through the following claim: According to common Hanafi view, definitiveness of proof, which signifies prohibition, is not necessary for determining haram; it can be equally determined through speculative proof. Thus, it is impossible to declare someone unbeliever unless he / she denies a haram with definitive proof.