Polish law defines marriage as a relationship between a man and a woman. Nevertheless, the European Court of Justice has recently ruled that the Polish registry office may not prevent the registration of gay marriages of Poles married in Germany. It followed the principle that if one EU member state allows something, the others must accept it regardless of their laws.
An obligation that member states would not agree to
This obligation is one of the cornerstones of the European project, despite the fact that it was not created by the democratic agreement of the Member States; they would hardly agree to such a denial of sovereignty. Almost half a century ago, it was imposed on the states by European judges to facilitate the emergence of the common market. Today, on its basis, they can change fundamental social institutions without democratic control.
It all began when, in the late 1970s, the German supermarket chain Rewe began offering its customers the French currant liqueur cassis. The catch was that, according to German regulations, fruit liqueur had to be at least 25% alcohol, whereas cassis contained only 15-20%. The authorities did not prevent the sale of cassis, but forbade the supermarket from selling it as 'liqueur', for reasons of consumer protection and to protect both consumers and German producers. By German standards, it was simply not a liqueur. Rewe launched a lawsuit and took the matter all the way to Luxembourg.
There, the judges ruled that such restrictions were contrary to the free movement of goods, the official goal of European integration to which all member states subscribe. In a landmark decision that has entered the textbooks of European integration, they defined the obligation of mutual recognition and made it possible to integrate even what the Member States would not have thought of.

