Being from the UK, I am not sure on all the rules around children and or guns.
However I am sure I have seen reports etc that suggest the registered gun owner is responsible and should keep both gun and ammunition securely.
In the same way we are told to keep medication securely locked away, tubs of dishwasher or washing machine tabs, powder or fluid should be kept out of reach of children in child proof tubs (which they are supplied in). All of which is common sense, so why are there so many injuries due to firearms, if these simple steps\ are being followed?