National constitutional courts have claimed to use the core of the constitution as a „sword” in order to strike down EU law provisions as inapplicable in that Member State. There are two constraints to such unilateral use of the protection of national constitutional identity. One follows from EU law’s interpretation of its own authority. The other concerns the legitimacy of such decisions and the role of courts in determining issues that belong essentially to the political domain.
(In Search of Limits for the Protection of National Identities as a Member State Interest în Between Compliance and Particularism: Member State Interests and European Union Law (coord. M. Varju), Springer, 2019, la p. 31)