The joint sitting of parliament cannot pass any bill under Articles 70 and 71 of the constitution. Perhaps the wisdom behind the separation of power of both houses of parliament that they enjoy through separate sittings was that the Lower House represents the people of Pakistan, while the Upper House represents the federating units, and so these different chemistries cannot intermingle.
Now, if, in the name of reconciliation, the government and the opposition develop some consensus in the matter and passed any bill in the joint sitting of parliament that will be considered a severe violation of the constitution.
Muhammad Aslam Badar
Faisalabad