Mr Sibal and the other petitioners have argued that mandatory enrolment under Aadhaar and linking the identification number to be able to access public and private services placed enormous information in the hands of the government.
Mr Sibal was also seen to counter suggestions that people could take remedial measures. "By the time, individuals come to court, years will pass and big brother will become bigger", he told the Constitution Bench of Chief Justice Dipak Misra, Justice AK Sikri, Justice AM Khanwilkar, Justice DY Chandrachud and Justice Ashok Bhushan.
During Wednesday's hearing, Justice Chandrachud suggested that there was need to balance national interest and right to privacy of citizens. "We live in times of terrorism, money laundering. One needs to balance out the privacy," he said.
Justice Chandrachud's remarks were a response to another senior lawyer for petitioner, Shyam Divan, who had argued that Aadhaar was nothing but electronic mapping of citizens. This does not happen in any other democracy in the world, Mr Divan said, arguing that individuals were free to lead life without constant gaze of the government.
But private operators such as Google also tap a similar kind of information, Justice Chandrachud asked.
"Google is not a State," responded Mr Divan. "Here government tracks you in real-time and it is police state... Our Constitution doesn't allow this. At just a click of a button, one can have profile of individuals".
Then it is a point about utilising the data collected, not the collection of data per se, the judge wondered. "Can we not make distinction of data collection and utilisation? That data collected shall not be used for purposes other than it is collected", Justice Chandrachud shot back.
The hearing will continue on Tuesday.