The Constitution also provides for the Council of Guardians, which is charged with examining all legislation passed by the Majlis to ensure that it conforms to Islamic law. According to Article 91, the Council of Guardians consists of twelve members; six of them must be "just and pious" clergymen who are chosen by the faqih or the Leadership Council. The other six must be Muslim lawyers who are first selected by the High Council of Justice, then approved by a majority vote of the Majlis. The members of the Council of Guardians serve six-year terms, with half the members being changed every three years.

The responsibilities of the Council of Guardians are delineated in Articles 94 through 99. The members must review each law voted by the Majlis and determine, no later than ten days after the assembly has submitted a bill for consideration, whether or not it conforms with Islamic principles. If ten days are insufficient to study a particular piece of legislation, the Council of Guardians may request a ten-day extension. A majority of the clerical members of the Council of Guardians must agree that any given law does not violate religious precepts. If the Council of Guardians decides that a law contradicts Islam, the bill is returned to the Majlis for revision. If the Council of Guardians decides that a law conforms with Islam, that law is ratified.