In the supranational legal order of the European Union it is of growing importance to keep intact the member States “constitutional identities”. This is clearly expressed, as a basic principle, by article 4 EU Treaty. The European Union as a community of States needs to respect the identities of its members. The concept of a “Union” requires as a basic condition that all the members of the Union remain intact in their statehood identity, and this means above all intact in the nucleus of their legal orders, namely in the basic elements of their Constitutions. EU membership (i.a. Poland) has as a consequence an adequate limitation of sovereignty, the integration of the national and supranational legal orders and the primacy of supranational law.