This thesis, called "Environmental principles and their application in international, EU and czech law", discusses the nature and application of the principles in the law generally, namely in international law, law of the European union and czech law. The first part of this thesis deals with the legally-theoretical definitions, the nature and basic characteristics and attributes of principles. The next chapters describes concrete environmental principles and their functions and occurrence in the law. Author attempts to show (through analysis of concrete normative documents a texts) the usage and application of principles in legal praxis. The importance of the principles is also emphasized from the point of view of concrete judicial cases, i...