The problem of correlation between normativism and sociology of law as Kelsen’s methodological grounds of law-understanding is examined. Elements of Hans Kelsen's «Pure Theory of Law» which characterized his constitutional understanding of law are analyzed:correlation between the validity of constitution and it’s effectiveness; Kelsen’s «effectiveness principle»’s influence validity of the constitution. Attention is drawn to the law substance of the legality of the constitutional changes principle.
The author presents a rationale that Kelsen’s normativism occupies a subordinate role in relation to sociology of law in the process of revolutionary changes of constitution. It is confirmed by the following tenets of «Pure Theory of Law»: effectiveness of constitution is a priority for its validity; force of constitutional legality principle is limited by revolution moment; principle of legitimacy is limited by the principle of effectiveness; Basic Norm may be repealed in case of its non-application during a long time. The article provides that sociological positivism is the necessary element of general law-understanding in the constitutional legal order’s change. The author’s conclusions are used while analyzing the changes of the Constitution of Ukraine.
It is shown that the Ukrainian Constitution’s changes in 2004, 2010 and 2016 were a «law revolutions». It is stated that contradiction between legality and legitimacy characterize not only periods of revolutionary change of the government, but are becoming feature of the whole constitutional process.
Keywords: normativism, sociology of law, constitution in action, effectiveness of the constitution, principle of effectiveness