As for the second pillar of their theory – the natural right to liberty – it is loosely understood as the absence of coercion, deceit, fraud, extortion and other sorts of deliberate effort to control the behavior of others, i.e., negative liberty. Libertarians appear to hold that a society with extensive negative liberty is all a person needs from the state to be self-determining. People are entitled to only as much self-determination as they can attain within the institutional framework of an unregulated free-market. But liberals look at it differently. They draw a distinction between the allocative function of markets and their distributive function.
One last point: Libertarians are well-known for objecting to governmental rules and regulations as yet another unnecessary restriction on people’s liberties. Sometimes they make the empirical point that regulatory bodies are open to capture by the very parties they are supposed to be regulating. No liberal would deny the point but that hardly shows regulatory bodies are necessarily bound to fail. More interesting is the conceptual point they sometimes appear to make: that regulations per se are restrictive of liberty. This is a dogma. Rules can liberate, provided they are intelligently made and judiciously administered. Just to take one example out of many, consider consumer protection laws. Given the technological complexity of the products consumers buy and the food and drugs they consume, it would be absurd to expect everyone to be their own safety control officer. Life is way too short for that. The information provided by properly done consumer protection laws can be highly liberating.
Contemporary libertarians may regard these arguments as shopworn and out of date. Maybe so, but I still hear them in political campaigns and the speeches of Congresspersons.