The interim constitution was that provisional document adopted by the national assembly on 17th April and enforced on 21th April 1972 which provided the guideline for running the administration of the country till 14th Aug 1972 when the permanent constitution of 1973 became operational. The emergency declared by Yahya Khan continued and Bhutto entered into the corridors of power riding on the horse of martial law. However, the political opposition could not let him behave dictatorially and tried to rein in his authority. So, a presidential order, National Assembly (Short Session) Order 1972, that authorized the assembly to draft the interim constitution before the permanent one.
The interim constitution provided for a presidential form of government. The president was required to be a Muslim of at least 40 years who was also the supreme commander of armed forces. The president elected for 5 years was assisted by a council of ministers each of which was required to be member of the national assembly. It means the constitution afforded a presidential system with a blend of parliamentary system as it made the cabinet or the council of ministers responsible to the parliament. Moreover, office of the vice-president was also given. A unicameral legislature empowered to legislate on all matters or subjects included in the federal and the concurrent lists.
Similarly, in the provinces a unicameral legislature was provided. The assemblies elected in 1970’s election were to constitute the provincial assemblies under the interim constitution. They were empowered to legislate on subjects written in the provincial legislative list and the concurrent list. Moreover, parliamentary system was introduced at provincial levels. Governor was the head of provincial executive aided by a council of ministers headed by the chief minister. The council was collectively responsible to the provincial assembly.
As for the Martial law, it was lifted with enforcement of the interim constitution but some specified martial law regulations and orders were deemed to have become Acts. The power for amending the constitution however vested in the president who was empowered to make such necessary adaptation required to put it into effective operation.
The day, the interim constitution was adopted by the national assembly a committee for drafting for drafting the permanent constitution was also constituted. Abdul Hafiz Pirzada was the chairman of this committee. Irrespective of all given difficulties, the permanent constitution was adopted by the assembly and replaced the interim constitution on 14th Aug 1973.