The article references the international cooperation of local governments, focusing primarily on cooperation counties, in the context of their implementation of the principles of sustainable development. The article characterises sustainable development within the meaning of international law and Polish law, in regard to the implementation of environmental protection. The authors also take into consideration to what extent and how effectively counties, through international cooperation, perform tasks in the fi eld of environmental protection whilst at the same time realizing the principles of sustainable development, and what barriers exist on that base. The authors therefore indicate legal and factual obstacles to international cooperation counties. The basis for discussion is primarily national and international legislation, and the authors, at the outset, determine the legal basis for international cooperation by Polish local government at county level for the protection of the environment and indicate the basic forms of this cooperation.