The question was raised by Pakistan's Chief Justice Nasir-ul-Mulk himself while hearing petitions challenging the procedure for appointment of superior court judges under the 18th Amendment and establishment of military courts under the 21st Amendment to try terrorists.
A 17-judge full court is hearing the case.
Mulk wondered if article 2 of the Constitution stating Islam as state religion can be replaced with secularism and asked could it be done by the present parliament or a Constituent Assembly would be needed, Dawn newspaper reported.
"Can a political party with unequivocal support in its manifesto to secularism, if given vast majority by the people, still be entitled to change the Constitution," asked Justice Main Saqib Nisar.
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The salient feature of the Constitution that "recognises Islam as a grundnorm (fundamental norm)" is not open to changes, he said.
The debate on secularism started when Justice Asif Saeed Khosa, while sharing his thoughts, observed that Pakistan had been created in 1947 in the name of Islam and it was declared that Islam would be the state religion.
After the formation of Pakistan, majority population from East Pakistan broke away and carved a new state called Bangladesh and framed a new Constitution by changing its basic feature to be secular.
Hamid Khan argued that only a Constituent Assembly could make changes in the Constitution.
Justice Nisar asked him to shed light on how the Constituent Assembly was formed; whether it could only be done through a revolution by annulling the present parliament and whether all the future generations could be made hostage to what the Constituent Assembly determined.
Khan said there was a consistent consensus in Pakistan that Islam should be state religion, adding that when the objective resolution had been adopted by the Constituent assembly in 1949, it was supported by all Muslim members but vehemently opposed by non-Muslim members.