Already the Weimar Constitution of 1919 contained fundamental rights which played an important role in labor law. However, there the fundamental rights only described a program to be implemented by legislation. The fundamental rights in the Constitution of Germany today automatically bind all three State branches and entitle individuals to enforce these rights in courts. The Constitution expressly only refers to the vertical application in the relationship between citizens and the State. Nevertheless, fundamental rights nowadays in Germany are considered to be the expression of values for the legal order as a whole. Therefore, horizontal application in the relationship between private actors has become important. The focus is not only the fundamental rights embedded in the German constitution but also on the very complex interplay with fundamental rights contained in European sources as the European Social Charter, the European Convention of Human Rights and the Charter of Fundamental Rights of the EU.