The referendum of May 2016 in the UK and the strengthening of a group of eurosceptics and nationalists in many European countries raises questions about the future of Europe and the European Union. The law is one of the areas of European integration. Already since the 70s of the twentieth century, the discussion about whether it should be unification or just the synergy of existing legal systems was undertaken. Eventually, the second concept won. The undoubted influence on this was made by the history of law, particularly the Roman law and medieval ius commune. At that time, the legal systems based on multiculturalism of law were created. Currently, there is the importance of a study conducted by comparative scholars developing various legal problems. They tend to build the foundations for the process of synergy of European law.