Casey doesn’t mess around:

States are criminal organizations. All states, not just the obviously totalitarian or repressive ones. […] I intend this statement to be understood literally and not as some form of rhetorical exaggeration.

The argument is simple. Theft, robbery, kidnapping and murder are all crimes. Those who engage in such activities, whether on their own behalf or on behalf of others are, by definition, criminals.

In taxing the people of a country, the state engages in an activity that is morally equivalent to theft or robbery; in putting some people in prison, especially those who are convicted of so-called victimless crimes or when it drafts people into the armed services, the state is guilty of kidnapping or false imprisonment; in engaging in wars that are other than purely defensive or, even if defensive, when the means of defence employed are disproportionate and indiscriminate, the state is guilty of manslaughter or murder.

Casey, Gerard. Libertarian Anarchy: Against the State (Think Now) (p. 1). Bloomsbury Publishing. Kindle Edition.

Clearly he is echoing Rothbard from For a New Liberty:

The libertarian, in short, insists on applying the general moral law to everyone, and makes no special exemptions for any person or group. But if we look at the State naked, as it were, we see that it is universally allowed, and even encouraged, to commit all the acts which even non-libertarians concede are reprehensible crimes.

The State habitually commits mass murder, which it calls “war,” or sometimes “suppression of subversion”; the State engages in enslavement into its military forces, which it calls “conscription”; and it lives and has its being in the practice of forcible theft, which it calls “taxation.” The libertarian insists that whether or not such practices are supported by the majority of the population is not germane to their nature: that, regardless of popular sanction, War is Mass Murder, Conscription is Slavery, and Taxation is Robbery.

The libertarian, in short, is almost completely the child in the fable, pointing out insistently that the emperor has no clothes.