The Harm Principle
According to Prof. James Stacey Taylor, John Stuart Mill’s harm principle has been one of the most influential political principles on classical liberalism. The harm principle states that the only reason to restrict the action of another individual is to prevent harm to others. If someone is harming themselves, you are only justified in attempting to persuade them. In theory, the harm principle has a lot to offer to those who frame laws. Unfortunately, it has not been thoroughly used in practice.