The contribution was presented by Koen Lenaerts, President of the Court of
Justice of the European Union, at a ceremony on the day of constitutionality
at the Constitutional Court of the Republic of Slovenia on 21 December 2017.
The author presents various aspects of the relationship between the national
constitutions and law of the European Union, which was developed primarily
through the case-law of the highest courts in the Member States and the Court
of Justice of the European Union. The author’s thesis, which is examined
and confirmed through the presented case-law of the Court of Justice of the
European Union, as well as the national constitutional and other courts, is that
national constitutions and the EU legal order complement one another. In the
process, the common constitutional traditions of the Member States, which
the European Court of Justice takes into consideration, had an important role
to play, even before they were expressly layed down as a guideline in the Treaty
on European Union and the Preamble of the Charter of Fundamental Rights.
Key words: Court of Justice of the European Union, constitutional law, judicial
control, fundamental rights, Judicial Network of the European Union