Justice M A Siddiqui issued notices to all seven convicts, seeking replies within four weeks.
The CBI in its petition is demanding the retrial of all seven for culpable homicide not amounting to murder under section 304-II of Indian Penal Code.
Assistant Advocate General Rashid Suhail Siddiqui said the trial court, in its judgement on June 7, 2010, convicted former Union Carbide chairman Keshub Mahindra, then Managing Director Vijay Gokhale, then Vice President Kishore Kamdar, Works Manager J Mukund, Production Manager S P Choudhury, Plant Superintendent K V Shetty and Production Assistant Shakeel Qureshi for "negligent act" causing death, under another part of section 304.
Advocate Siddiqui said that trial should be conducted afresh for culpable homicide (a more serious offence which attracts 10 years in jail).
Over 3,000 people were killed after poisonous gas leaked from Union Carbide's pesticide plant in Bhopal on the night of December 2-3, 1984.