I was reading someone complaining about a proposed law on gun ownership in California; he said he had this nightmare vision of a future in which only the police and the criminals had guns. Strangely enough, my nightmare vision would be the exact opposite. Quite apart from the practical dangers associated with having guns in the house- accidents and domestic disputes; there's also the question of suicide. One of the surprising but consistent findings of research into suicide attempts is that, rather than having made a firm decision to die the suicidee chooses a method and carries it out, they are rather in a state of not minding either way. This leaves libertarians like me in a dilemma, since we would endorse the right of those who wished to kill themselves to do so, but would nevertheless be obliged to try to prevent them in case they hadn't quite made their mind up. [Attempting suicide is still treated by many countries as a crime (because you are robbing the state of your contribution to it); according to my son, they take a very dim view of it, and they sentence repeat offenders to death]
But crime is where it matters most. Guns change things. Almost all interactions with others are bound by social norms as much as anything. This is why a small old woman can scare away a crowd of teenage yobs: although they could easily physically overpower her, their brains respond with instinctive respect for an older person who is in the right. A weaker version of the same moral force allows teachers to subdue unruly classes. It is this moral force which keeps the law. That's why riots are followed by copycat disturbances: people suddenly relaise that there is very little that the few police can do to enforce the law. Chesterton says somewhere that the countryside is full of sin, because of the absence of others to observe. But put a gun in the equation and social factors are set aside.