The purpose of the article is to test the relevance of the requirement of good faith in the application of the Constitution. Starting from the observation that the requirement of formal regularity is not sufficient to avoid the instrumentalization of the Constitution, it envisages supplementing it with a substantive requirement of good faith in the execution of the constitutional provisions. The latter would make it possible to cover a whole range of situations that are formally regular but which, in reality, aim to circumvent the constitutional provisions in force. In the first instance, the article seeks to objectivize the requirement of good faith, abandoning the use of generic categories of values or general quality of behavior, tinged with a strong axiological dimension, to identify categories of specific behaviors likely to concretize the requirement of good faith execution in the Constitution. In the second instance, the article aims to test, by means of a practical test, the relevance of resorting to good faith. The latter appears difficult to mobilize objectively in, what we will call, “border cases”. Above all, it raises the question of the subjectivity of the assessment of the actors of constitutional law as well as that of the establishment of mechanisms for sanctioning respect for good faith which can result in a transfer of political subjectivity from the organs of power to the judge. From our point of view, the requirement of a good faith execution of the Constitution illustrates the limits of the juridicisation of virtuous action.