There are also questions about its cost. A top administrator with the Illinois Department of Corrections says the state's prison system is already stressed. Bryan Gleckler says this would add another three thousand inmates over the next decade.
"We do not have capacity for a population increase of 3,000 inmates. There is no capacity to take this additional population on."
Gun rights groups are also opposed. They say the penalties are too stiff for otherwise law-abiding gun-owners who just make a mistake.
The measure's sponsor tried to address those concerns. First-time offenders will be treated more leniently than ex-felons caught carrying a gun. Advocates say the threat of a longer prison sentence will deter gang members and reduce crime.