Abstract
In this paper I outline a theory of legitimacy that grounds the state’s right to rule on a natural duty not to harm others. I argue that by refusing to enter the state, anarchists expose those living next to them to the dangers of the state of nature, thereby posing an unjust threat. Since we have a duty not to pose unjust threats to others, anarchists have a duty to leave the state of nature and enter the state. This duty correlates to a claim-right possessed by those living next to them, who also have a right to act in self-defence to enforce this obligation. This argument, if successful, would be particularly attractive, as it provides an account of state legitimacy without importing any normative premises that libertarians would reject.