According to art. 91 paragraph 3 of the Constitution, if it results from the agreement (ratified by the PolishRepublic) establishing an international organization, the law established by this agreement shall be applied directly and shall have precedence in case of conflict of laws.

Polish accession to the European Union meant that the Union's legal system became a system of its own in Poland and that in its territory there is legal order including system of national law and the entire oeuvre of Community law. (E. Łętowska, Multicentricity of modern system of law and its consequences, ”State and Law”, 2005, no. 4, p. 7).

From 1 May, 2004, the Republic of Poland, on the basis of article 2 of the Accession Act, which is an integral part of the Treaty signed on 16 April, 2003 in Athens (Journal of Laws 2004 no. 90 pos. 864) is bound with: firstly, the provisions of the founding treaties including the Treaty establishing the European Community ( Journal of Laws of 2004 no. 90 pos. 864 / 2) as the primary Community law; secondly, the acts adopted by the Union institutions (secondary Community law) and thirdly, what is somewhat new, the interpretation and application of Community law resulting from the ECJ. All these elements constituting Community law, in force even before the accession, is known as acquis communautaire. Hence the obligation to apply Community law in domestic legal order. The obligation is incumbent not only on national courts, but also organs of administration. (Verdict of the Supreme Administrative Court of 10 February, 2010, FSK II 1450/2008).

European primary law (treaty), is characterized by, inter alia, the following features: priority (supremacy) and the direct effect of standards (direct effect). These features are widely regarded as a system policy of the Community legal order, (C. Mik: European Community law. Issues of theory and practice. Volume I, Warsaw 2000). Primacy of Community law means that "when the law of a Member State is incompatible with (immediately effective) Community law, the court of a Member State is obliged to resolve those conflicts in accordance with the principle of priority defined by the European Court of Justice" (A. Wrobel, Introduction to the law of the European Communities (European Union), Cracow 2004, p. 145).

It is emphasized in doctrine and jurisdiction, that the direct effect is caused by these provisions of Community law, which: 1) are clear and precise, 2) are unconditional, 3) do not confer to Member States or Community institutions the powers to act on the principle of discretion, if they shall be enforced by these bodies. One of the elements of the EU legal order is directives which proper implementation is the responsibility of the Member States. It is important to take such adjustment measures which will correspond to the essence of the directive and adapt to its purpose, in other words, the implementation should faithfully reflect the spirit and purpose of the directive.

Within the competence of the judicial bodies, the ECJ enumerates assessment of the proceedings of legislative and executive bodies and realization of individual rights arising from the directives. In particular, according to the ECJ, after the directive comes into effect, judicial authorities are obliged to check whether the actions of other bodies do not pre-empt or pose a serious threat to timely achievement of the result prescribed by the directive.

Starting from 1 May, 2004, that is from PolishRepublic's accession to the European Union, because of the principle of interpretation of domestic law to allow smooth functioning of the economy within the European integration, interpretation of law should be made in compliance with European law (ECJ verdict of 13 November 1990 Marleasing C-106/89 ECR. s I-4135). It is the obligation for ensuring the compatibility of domestic and European law (Article 5 TEC), and it affects all EU countries.

In support of its ruling of 21 September, 2004 (C 34/2003, OTK ZU 2004/8A, item. 84), the Constitutional Court pointed out that the above obligation causes that the results of interpretation of domestic law leading to the result different than under Community law can not be endorsed.