Article 9 of the Polish Constitution establishes the obligation of respect by the Republic of Poland of international law binding upon it. This provision belongs to the fundamental principles of the Polish legal system. However, it cannot be excluded that the interpretation or application of an international agreement, to which Poland is a party, will be changed by other parties or organs of an international organisation without consent of Poland. It could cause the conflict with principles or paticular provisions of the constitution. The case law of the European Court of Human Rights and the Court of Justice of the EU, leads to the conclusion that for a certain period of time, state authorities of Poland, by legislation or interpretation, attributed to provisions of the Polish constitution the meaning incompatible with their understaning at the moment of the accession of Poland to an international agreement. The protection of the supremacy of the constitution “modified” this way is equivalent to the use of an unconstitutional interpretation in order to free government from obligation to respect international law binding upon Poland.