Libertarian theory has scantly been applied in an international context. With an ever-growing emphasis on globalization and the need to resolve arising conflict, it seems as good a time as any to put foundational libertarian theories to the test. Arguably, the foundational theory of libertarianism is the non-aggression principle. The non-aggression principle asserts that one may not aggress against another or their property. If aggression does occur, the aggresse has rightful recourse. But such theory has one flaw—not all violations of property rights are protected by the non-aggression principle. Thus, a broader theory is imperative. Building on the work of Billy Christmas, by shifting the non-aggression principle to the non-interference principle, libertarianism can incorporate all acts against property rights. With respect to international relations, the non-interference principle can act like a guide to States. This essay applies the non-interference principle to the contemporary Iran—Afghanistan conflict. Applying the non-interference principle demonstrates both that libertarian theory is not purely academic as some critics assert and that it can address pertinent complex international matters.