Harry would also do some very creative things with Dobby. If "a house elf that is bound to a wizard is also bound by wizard laws", that implies that a house elf that is not bound to a wizard is not bound by wizard laws. For instance, anti-apparition wards usually allow house elves to pass through them so the household staff can move around unseen; other families’ elves are still unable to trespass because they are bound by wizard law. But Dobby isn’t, so he can pretty much go anywhere and do anything, and nobody really thinks about house elves or notices their presence.