The idea of European integration and frequently also subsequent unification of law in Europe may seem to be quite a recent topic. If it is talked about, it is more or less in scope of decades, or with regards to the recent change of era, it might be considered no earlier than a last century issue. However, the roots of European integration can be found, without any doubt, much earlier; namely at the time when the Roman Empire had not only been forming the European organization for many centuries, but also the history of part of the territory of African and Asian continent. Although the motivations of their masterminds were different, we encounter some efforts to assure durable peace through peace treaties between those who really wanted to achieve it. First agreements of this type – putting peace under penalties of international legal nature, were already known in Old age.