The author analyzes the general principles of law in constitutional adjudication. This phenomenon is considered in the light of the doctrine of constitutional identity spreading in the legal academia and practice of the Constitutional Court of the Russian Federation. The article consists of two parts. The argument is advanced in first part of a paper that those principles applied in constitutional adjudication through using the legal Latin. Special attention is paid to international law. A distinction is made between international custom and the general principles. The thesis is substantiated that, the essence of the general principles of law is in their definition as unwritten law. From historical point of view, the general principles of law are unthinkable outside the natural law as a type of legal philosophy. The main points of the presented paper are illustrated by the example of the proportionality principle.