Chief Justice Iftikhar Muhammad Chaudhry on Saturday constituted a five-member bench to hear petitions challenging parts of the 18th Amendment. Headed by Justice Nasir Ul Mulk, the bench comprises Justice Raja Fayyaz Ahmed, Justice Jawad S Khawja, Justice Rehmat Hussain Jafferi and Justice Tariq Parvez. The bench will take up the petitions on April 28. The separate petitions filed by Supreme Court Bar Association, Ralwapindi Bar Association and Ejazul Haq challenged the Supreme Judicial Council and certain other parts of the 18th Amendment. The petitioners argued that present Parliament is not a constituent assembly, and therefore it did not have the mandate to change the basic structure of the Constitution.