Hans kelsen

State is nothing but a system of human behavior and order of social compulsion. State and law are the same according to Kelsen and he rejects dualism.
In every legal system, there is existence of hierarchy of 'ought'. Among such ought, some are fundamental from which all others emanate. This is called grundnorm. (Basic source of law is another law which leads to hierarchy of law)
A grundnorm is said to be accepted when it has secured for itself a minimum level of effectiveness. When it ceases to derive a minimum of support, it ceases to be the basis of the legal order. For that reason, it is replaced by some other grundnorm that obtains minimum support. (Pyramidal structure of hierarchy of norms = 'Concretization')