Most likely you are speaking of pistols and NYC residents can still own guns. However, Guiliani did not create laws making handguns illegal in any case. Executives must execute the laws enacted.
The vast majority of guns confiscated were those of criminals. The others are regrettable.
A nameless, faceless bureaucrat many years ago: "All men, women, and children must report to zee showers, mach schnell!"
"Vee are not concerned with exterminating zee adults, but...
zee 'others are regrettable'".