The free movement of goods is one of the four freedoms of the Internal European market and is ensured by the Treaty on the Functioning of the European Union. In addition to the free movement of goods, the free movement of workers, services and capital is included. Four freedoms represent the very core of European law. The European integration is based on Internal Market integration, and today that process has outgrown its primarily economic significance. It has gone deep into all the pores of social importance. The Internal Market of the European Union is an area of free movement reinforced by a customs union in which trade tariffs are eliminated, and quotas are removed between Member States with a joint agreement on the level of tariffs on goods coming to the market from third countries, with the addition of free movement of production factors, labor, and capital. In general, European law, in its entirety, remains an evolving organism, with the scope governing the Internal Market serving as a vivid example. The European Court of Justice regularly interprets and applies the laws related to it, influencing how it develops. So, the main goal of this thesis is to show that the Internal Market is always changing, evolving and getting more functional. This emphasizes how crucial it is to follow the rules and principles to make sure that the Internal Market works smoothly. Therefore, the analysis focuses on examples of legal cases which establish the balance between the need for clear rules for companies and customers, and the goals of market integration in the European Union.