The subject of this article is to explain and analyze the viewpoint of the Guardian Council regarding the scope of the Islamic Consultative Assembly’s competence in the position of interpreting the law. The question is to clarify the limitations derived from the viewpoint of the Guardian Council as the interpreter and supervisor of the Constitution, which the Islamic Consultative Assembly as the interpreter of ordinary laws is confronted. The research methodology is descriptive-analytical method. The review of the Guardian Council's decisions indicates that in the viewpoint of this Council, the jurisdiction of the Islamic Consultative Assembly isn’t absolute. The Guardian Council, through its interpretative opinion on 22/1/1/22, declared that new legislation by the Assembly during the interpretation of law is inconsistent with principle 37 of the Constitution while such prohibition isn’t understood from that principle. From the perspective of the Guardian Council, retroactivity of the Assembly's interpretation of laws is restricted to the cases that are not concluded. Respecting to the acquired rights is another limitation for the Assembly in interpreting the law. Besides, Assembly's accurate interpretation of laws, sometimes, contains no new legislation, but due to the Assembly’s interpretation, it is revealed that the primary law has been contrary to the Constitution or Islamic law and therefore, it is declared as inconsistent with the Constitution or Shari’a (Islamic law).