The first part of this article presents an analysis of the constitutional basis of membership of the Czech Republic in the European Union. Particular attention is paid to amendments introduced to the Czech Constitution (they came into force in 2002). These amendments not only established a basis of the Czech Republic's accession to the EU, but also made Czech legal order similar to the monistic model of reception of international law. This part also contains remarks on the position of the Czech Republic within the European Union. The second part of the article discusses two fundamental judgments of the Czech Constitutional Court - of 8 March 2006 on the so-called sugar quotas and of 3 May 2006 on the European Arrest Warrant. In these judgments the Constitutional Court addressed many issues connected with the EU membership and their consequences for the Czech domestic legal order. The authoress points out, in particular, the issue of validity of Community law in that legal order and - in this context - the discussions on this subject presented for some years in major Czech law journals. The conclusion of an analysis of the above-mentioned judgments is that the Czech Constitutional Court has formulated a Community-law-friendly doctrine, declaring the need for respect of the precedence of Community law, but without unconditional acceptance thereof. The scope of such acceptance by the jurisprudence of the Czech Constitutional Court, and that of appropriate bodies appointed to review constitutionality of legal acts in other EU Member States (including Polish Constitutional Tribunal) are similar and determined by the following elements: State sovereignty, inalienable rights of the person, the principle of democratic state ruled by law. On the one hand, the Czech Constitutional Court seeks inspiration in the jurisprudence of other constitutional courts, on the other hand, it makes courageous attempts, e.g. to assess the standards of respect of human rights in the EU countries, which - in the view of that Court - are not lower nor different from those available to the citizens of the Czech Republic.