You are not liable in law for anything you sell in that respect. whether you sell in locally or anywhere else the wrong person could end up hurting someone or killing the neighbours dog. It isnt the weapon that kills, its the person behind the weapon.
You'd only be liable if you knowingly sold them to be used for illegal purposes, so you are not liable if you sell them and they are used for illegal purposes unless the person told you they were buying them to go and shot somebody that had annoyed them (or similar)