The classical principle of cooperation in environmental protection which has been embraced in international law continues to be of key importance. Yet, in international environmental law, particularly in climate protection law, one can see a tendency emerging towards the development of the solidarity paradigm as a catalyst facilitating the uptake of the principle of qualified cooperation of states to protect the common concern of humankind.
In the doctrine, there is a quite common belief that the concept of a general principle of solidarity is used as a prerequisite for effective environmental protection (see e.g., P.G. Carozza, L. Crema, On Solidarity In International Law, Caritas In Veritatis Foundation, 2019 p. 3 ff.). In general terms, as a principle of international environmental law, solidarity involves the recognition as a legal norm of the behaviour based on the belief that each member of the international community which uses the benefits of the protection of the good (the environment) by the entire international community acts with the conviction that by protecting common goods it protects individual goods.
The practice of international relations provides the ground for placing the principle of solidarity within the structural dimension of the general principles of international relations, which affect the structure and content of international relations, and thereby the implementation and effectiveness of environmental law. Examples of the effectiveness of the application of such a perspective include the restriction on the complete freedom of a state to dispose of its resources as introduced by the environmental imperative of environmental protection in international relations and the principle of responsibility for the conservation of the environment for the future generations (see D. Shelton, Equity, in: D. Bodansky, J. Brunee, H. Hey, The Oxford Handbook of International Environmental Law, Oxford 2006, p. 640 ff.).
International environmental law refers explicitly and implicitly to the principle of solidarity in various types of documents and legal acts. In the literature on the environment, examples of the cases related to the origin of the development and application of the solidarity standards primarily refer to the context of the principles addressing the environmental damage in other states (see e.g. the Trail Smelter case: Trail Smelter Arbitration, United Nations v. Canada, 1941, 3RIAA, 1905) or the Lake Lanoux case (Lac Lanoux Arbitration, France v. Spain, 24 ILR 101, 1957.) The theses of the decisions of arbitration courts in these cases were later expressed in the content of Principle 21 of the Declaration of the 1972 United Nations Conference on the Human Environment (the Stockholm Declaration), repeated in Principle 2 of the 1992 Declaration on Environment and Development (the Rio Declaration), and also in the Draft Global Pact for the Environment (Article 5). The practice of states demonstrates that the concept of the principle of solidarity in international environmental law has been expressed in different forms, in the processes of law making, compliance with law and its enforcement.
Another example of the effectiveness of such an approach to the concept of solidarity is the principle of cooperation of states, which is one of the fundamental systemic principles of contemporary international environmental law. It has been expressed by the principles laid down in the provisions of Principles 21 and 22 of the Stockholm Declaration, Principles 5, 7, 9, 12, 14 and 27 of the Rio Declaration, the provisions of the 1979 Geneva Convention on Long-Range Transboundary Air Pollution (18 ILM 1442), the provisions of the 1985 Vienna Convention for the Protection of the Ozone Layer (26 ILM 1529), the provisions of the 1992 United Nations Framework Convention on Climate Change (31 ILM 849), the 2015 Paris Agreement on Climate Change and the 2017 Draft Global Pact for the Environment. A review of those provisions indicates a tendency emerging towards the development of qualified standards of international cooperation based on reference to solidarity.
An example of a clean reference to the concept of solidarity in environmental law is the development of the concept of sustainable development, based on the principle of intergenerational and intragenerational equity and the general belief that misuse of the environment in a manner depriving the future generations of the ability to satisfy their needs and aspirations is the choice of the wrong development alternative which is inconsistent with the principle of global justice (see E. Brown Weiss, Our Rights and Obligations to Future Generations, AJIL 1990, Vol.84, passim).