Libertarianism ≠ NAP
Anarchists masquerading as "Libertarians" or "Voluntaryists" most often promote a philosophical concept they have coined as the "Non-Aggression Principle" (aka: "NAP") to be the only principle of so called "libertarianism" upon which all political and social issues can be ideologically addressed.
According to what best advances their self-refuting fantastical agenda of society without [government], they often selectively define the word "aggression", ranging from the use or threat of physical violence to the imposition of civil laws governing risk of Natural Rights violations (for example, traffic regulations). This vagueness in and of itself refutes the anarchist claim of libertarianism being solely equated with the "NAP".
The article entitled "Six Reasons Libertarians Should Reject the Non-Aggression Principle" by Matt Zwolinski on www.libertarianism.org reveals some of the philosophical shortcomings of the "NAP", as well as its incapability of addressing every problem in society. In reason #6 Matt makes a profound statement regarding the true principles of "libertarianism", broadened to its logical extent as follows:
Fundamental to libertarianism is the enforcement of Natural Rights through the Rule of Law
(Not the Prohibition of Aggression)
To the extent Civil Law honors Natural Law protecting individual Natural Rights, aggression by any definition is minimized or eliminated altogether.