By studying legal texts, doctrine and jurisprudence of Iran, several examples can be found in which non-opposability, not as proof of the dispute, but as existence of legal elements, has been talked about. This concept of non-opposability, that is a kind of legal sanction, despite the reflection and use in domestic law, remains unclear and no exact conceptualization has been made. Moreover, the position of this sanction, along with other legal sanctions in the domestic system, is not clear, and as a result of this ambiguity, the effectiveness and application of this sanction in domestic law, due to the confusion of this concept with existing concepts, has sometimes been questioned or rejected. This study seeks on the one hand by defining the concept of non-opposability in its origin, it means French law, clear this concept in Iran law and on the other hand, by comparing this legal institution with similar concepts and the distinct boundaries of concepts, explain the position of this sanction in domestic law and prevents from confusion of existing concepts in this field.