Two forms of «neo-constitutionalism» can be distinguished: a polemic form and an adaptive form. The first type is a doctrinal movement which aims to criticize the positivistic basis of constitutional law and stress the role of principles and values. The second form maintains a strong positivistic stance. This paper argues that the distinction between these two types of «neo-constitutionalism» does not mean that they are incompatible. A common reference can be found in Kant’s «universality test» that is based on a subjective universalism. The supreme principles of the constitutions are maxims that could be considered by all rational beings as universal laws of action. «Polemic neo-constitutionalism» recognizes the crucial role of the interpreters of the constitution, whereas «adaptive neo-constitutionalism» emphasizes that the distinction between law and morals is contingent upon a series of parameters.