Permissibility or prohibition of some of the Halal products is, in many cases, doubtable. It is because there is no ruling or there is an ambiguous judgment or a conflict between two rulings which is called as al-shubhat al-hukmiyah or as a result of confusion in external instances, which is named as al-shubhat al-misdaqiyah."The rule of permissibility (Hell)" in such cases can be regarded as the primary principle for determining Permissibility or prohibition ruling of General Obligation (al-hukm al-taklifi) or even ruling of Situation (al-hukm al-Wazie) in these cases. The author of this paper explains this principle and examines its differences with other jurisprudential rules, such as "the principle of exemption" (al-baraah) and "the continuity of permissibility" (al-istishab). Then explains its contradiction with other practical principles. Finally it is considered carefully the reasons for this rule and its scope.