The libertarian theory of law, as a non-positivist conception of law, defends the separation of morality and law thesis, a thesis that is typically positivistic. The question of the relationship between morality and law is a part of the validity of law problem, which refers to the fundamental issues of legal ontology: the grounds for the validity of law, the role of coercion in law, etc. Different answers to these and other relevant questions cause fundamental distinctions between two traditions of legal thought - natural law and positivistic. The answers that can be obtained within the framework of the libertarian theory are of great interest in connection with the thesis of its synthetic nature. In the question of the interpretation of the existence of law and the grounds of its validity, the libertarian theory denies the social thesis of legal positivism and stands on Proceedings of the Institute of State and Law of the RAS. 2018. Volume 13. No. 4 Разделительный тезис либертарно-юридической теории… 59 the position of realism (in the logical sense of this concept), according to which law in its distinction with statute is an objective ideal entity, existing before positive law, along with it, and appearing in it. The question of correlation between Is and Ought is considered in the libertarian theory in genetic and ontological aspects: if it gives a contradictory answer to the genesis of the essence of law, then in the ontological aspect Ought - the principle of formal equality - certainly determines the sphere of Is, which is formed by positive law and state. The universal principle of formal equality, as specific to the law and distinguishing the law from other normative orders, is the basis of the validity of positive law. At the same time, the analysis of the libertarian theory leads to the conclusion of the identity of law and human rights, and consequently, it is human rights that form the basis of the validity of positive law. The separation thesis of the libertarian theory means that the basis of the validity of a positive law cannot be one or another system of morality, therefore, the immorality of a positive law does not deprive it of legal validity. However, the author believes it is possible to talk about the moral foundations of the principle of formal equality. In the libertarian theory, coercion is understood exclusively as physical coercion - a “force” assigned to law by state. The basis of the validity of positive law - the principle of formal equality - is also the basis of the legitimacy of coercion, allowing it to be differentiated from the illegal use of force - violence. Based on the model of dualism of law and state, the libertarian theory emphasizes their necessary connection: the state is considered as a servant of law - liberty, human rights. The libertarian theory, taking into account its interpretation of the grounds of the validity of the law, can be attributed to the tradition of natural law, in the development of which it has made an outstanding contribution - natural law has finally acquired its legal character. It can be described as a monistic deontological anthropocentric theory of natural law with historically changing content.