There are few cases where gun-bearing individuals have stopped crime, and it is nearly impossible to find many cases of guns deterring crime.  The cases of Gabby Giffords and the Columbine shooters are prime examples of failure.  If you compare this to the number of killings facilitated by guns, the decision is a no-brainer.  There is little possibility of a serious court challenge: even the misguided Heller decision states that it is not intended to restict a state's right to prohibit the types of firearms that people can purchase or the places where they can be taken.