Public International Law/International Environmental Law





Author: Abbas Poorhashemi Required knowledge: Public International Law

Learning objectives: This chapter book aims to discuss and present the essential elements of the foundation and emergence of international environmental law as a new branch of international public law. Furthermore, it tries to provide some knowledge of the sources and principles of international environmental law. Environmental challenges such as climate change, desertification, air pollution and sea pollution are amongst the most urgent that require an immediate and collective response from the international community. Understanding the opportunities and challenges facing the international community is crucial for the future development of international environmental law. In this perspective, the learning objectives of this chapter include understanding the basics and emergence of international environmental law as a new branch of general international law, exploring the essential elements and fundamental principles of international environmental law, identifying and reviewing its sources, developing knowledge about ecological challenges facing the international community, understand the relationship between environment, sustainable development and preservation of the global climate and finally, understand the importance of international cooperation and collaboration to address environmental challenges.

Introduction
The relationship between humans and the environment has been discussed and investigated from different points of view. Many jurists disagree about whether this relationship can be examined from a legal point of view, and some even go so far as to refer to international environmental law as global ethics. But looking at the formation and development of international environmental law in the last decades, it becomes clear that this field, as one of the branches of public international law, has been able to include principles and rules. Important for managing, protecting and protecting the environment led to the creation of binding regulations, such as concluding more than a thousand bilateral and multilateral treaties, compiling international custom, international judicial procedures, etc., as well as developing non-binding instruments, such as statements, resolutions, recommendations, etc.

By applying an interdisciplinary or multidisciplinary approach, international environmental law has developed at national, regional and global levels. Since the environment has no boundaries and all humanity is on a single ship called the Earth, any damage to this ship will cause the destruction and decay of the entire human society. This emerging field in international law has taken the non-binding rules that did not have a place in classical international law in the service of its development and expansion and shown how these non-binding tools could be turned into codified and enforceable legal principles. In the shadow of the development and expansion of this legal field, the right to a healthy environment, the common heritage of humanity, the rights of future generations, and the right to development were crystallized as examples of environmental human rights. Therefore, this chapter is primarily compiled for researchers, students and international environmental law scholars, giving an overview of this field.

A. Emergence of International Environmental Law
Some sources define “environment” as the air, water, and land in or around which people, animals, and plants live. The environment is a balanced set of biotic and abiotic elements that surround a body and can interact with it. The concept of “environment” includes (but is not limited to) spaces, resources, natural land and marine environments, sites, day and night landscapes, air quality, living beings and biodiversity, biological processes, soils and geodiversity. There are various definitions of "international environmental law". According to the definition given by Alexander Kiss and Dina Shelton, international environmental law is one of the newest branches of public international law, which aims to protect the environment. Some also define international environmental law as a set of rules of international law which the purpose is to prevent environmental pollution and to protect the environment. While the above definitions are acceptable, they are not comprehensive. It may seem that international environmental law is a body of international law concerned with protecting the global environment by applying legal norms and regulations that address transboundary, regional, or global environmental issues.

International environmental law as a branch of public international law emerged in the 1970s. In fact, the 1960s, known as the decade of student movements (women's, green, and postmodernism), interrogate the destructive process of modernity, among others, the environment. After that, environmental experts and scientists announced that the world would be destroyed if industrial progress and economic growth continued in this direction. As a result, until the end of this decade and the beginning of the seventies, they forced the respective governments to hold the Stockholm Conference. The Stockholm Conference of 1972 was a turning point in drafting and developing international environmental law by recognizing the right to a healthy environment as one of the fundamental human rights and the close relationship between development and the environment. Since then, environmental protection has become a significant concern and preoccupation of the international community. Climate change, air pollution, lack of safe drinking water, hazardous wastes, soil erosion, loss of biodiversity as well as noise and light pollution are the global challenges of humanity. To respond to these environmental challenges, the international community has recognized the need for holistic and expansive environmental protection. Moreover, the international community has become aware that local issues are interconnected with national, regional, and global conditions.

At the United Nations Conference on the Environment in Stockholm in 1972, environmental protection was the subject of several treaties and declarations which illustrate the willingness of the international community to protect the environment, encourage sustainable development and attenuate the imbalance between the North and the South. These conventions accepted and ratified by States could be considered global responses to contemporary environmental problems. Moreover, international environmental treaties unite developed and developing countries by ensuring that developed countries “assume their historical responsibility” for global environmental degradation.

Some of the leading environmental conventions are:


 * Climate change: Vienna Convention for the Protection of the Ozone Layer (1985), Montreal Protocol (1987), United Nations Framework Convention on Climate Change (UNFCCC) (1992), Kyoto Protocol (1997) and 2015 Paris Agreement on climate change.
 * Environmental Accidents and Civil Protection: Helsinki Convention on Industrial Accidents (1992), Barcelona Convention (1976), Helsinki Convention on the Baltic Sea (1992), OSPAR Convention (1992), Bonn Agreement (1983), Lisbon Agreement (1990), Convention on the Protection of the Black Sea Against Pollution, Bucharest, (1992), Helsinki Convention on Industrial Accidents (1992).
 * Biotechnology and Chemicals: Cartagena Biosafety Protocol (2000), Stockholm Convention on Persistent Organic Pollutants (2001), Rio Convention on Biological Diversity (1992) and its Supplementary Protocol on Liability and Redress (2010), Rotterdam Convention on Prior Informed Consent (1998), Minamata Convention on Mercury (2013).
 * Human rights and environment: Aarhus Convention on access to information, public participation in decision making and access to justice in environmental matters(1998),Protocol on Pollutant Release and Transfer Registers (2009), and the Espoo Convention on Environmental Impact Assessment (1991).
 * Biodiversity: Convention on Wetlands of International Importance, Ramsar, (1971), Convention on International Trade in Endangered Species of Wild Fauna and Flora, (known as CITES Convention) (1973), Bonn Convention on the Conservation of Migratory Species CMS (1979), Convention for the protection of vertebrate animals used for experimental and other scientific purposes (1986),Bern Convention on European Wildlife and Habitats (1979), Convention on Biological Diversity CBD (1992), International Tropical Timber Agreement (ITTA) (1994), Agreement on the conservation of African-Eurasian Migratory Waterbirds (AEWA-CMS) (1995), Alpine Convention (1991), Cartagena Protocol on Biosafety (2003), Convention for the Conservation of Antarctic Marine Living Resources (1980), Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of the Benefits arising from their Utilization, Nagoya (2010) and Agreement on the Protection and Sustainable Development of the Prespa Park Area (2010).
 * Water protection: Barcelona Convention (1976) and its protocols, Bonn Agreement (1983), Danube river basin convention (1987), Helsinki Convention on Watercourses and International Lakes (1992), OSPAR Convention (1992), Convention on the Protection of the Black Sea Against Pollution, Bucharest (1992), Helsinki Convention on the Baltic Sea (1992), Rhine river basin convention (1999).
 * Some of the non-binding international instruments to protect the global environment are the United Nations Conference on the Human Environment, 5-16 June 1972, Stockholm, the World Charter for Nature of 1982, Rio Declaration on Environment and Development (1992), Agenda 21 UNCED, 1992,  United Nations Millennium Development Goals (2000), Johannesburg Declaration (2002), Rio+20 Declaration (2012), the 2030 Agenda for Sustainable Development (2015) and the 17 Sustainable Development Goals (SDGs).

Although these conventions have been signed, accepted and ratified by the majority of the States, the commitments made by the States seem minimalist and insufficient concerning the gravity of problems and challenges facing the development of international environmental law.

B. Generations of International Environmental Law
International environmental law is developing as one of the branches of public international law. Although the conservation of some species of animals and plants dates back to the pre-1970s, the basis for the formation of international environmental law, in its modern concept, is the Stockholm Declaration of the United Nations Conference on the Human Environment in 1972. In general, international environmental law is historically divided into three periods.

I. First generation: before the formation of international environmental law until the 1972 Stockholm Conference
The first generation began mainly in the 18th century with the signing of especially bilateral agreements in the field of fisheries and marine life resources. The most important feature of this historical period is regionalism and the creation of contractual obligations between governments to protect a specific region or species. For instance, the Treaty concerning the Regulation of Salmon Fishery in the Rhine River Basin on June 30, 1885, the Paris Convention for the Protection of Birds Useful to Agriculture on March 19, 1902 , the Treaty relating to the Boundary Waters and Questions arising along the Boundary between Canada and the United States done at Washington on January 11, 1909 , for the protection of the Great Lakes and the Convention for the Protection of Migratory Birds in Canada and the United States on August 16, 1916 , and Convention relative to the Preservation of Fauna and Flora in their Natural State on November 08, 1933 , are some examples of this period. Its expansion to other fields, including wildlife, rare and endangered plants and animal species, continued into the early twentieth century. The most important feature of this historical period is its regionality and the creation of contractual obligations between states to protect a particular region or species. The 1960s, generally known as the decade of student movements (the women's movement, the environmental movement, and the postmodern movement), marked a turning point in the destructive process of modernity and addressed many fundamental issues, including environmental matters. Subsequently, environmental activists and scientists declared that if industrial progress continued the same way, the world would be destroyed. As a result, by the end of the decade and the beginning of the 1970s, states were forced to hold the Stockholm Conference of 1972. The Stockholm Conference of 1972 recognizes the right of development to be closely linked to the environment by identifying the right to a healthy environment as a fundamental human right. Furthermore, by considering the establishment of international institutions, it integrated the process of global cooperation in the field of the environment. It provided the direction for the further development and evolution of the relevant international rules to protect the global environment.

II. Second generation: from the Stockholm Conference 1972 until the Rio Conference 1992
According to the recommendation of the United Nations General Assembly, the International Conference on the Protection of the Environment was held from 5 to 16 June 1972 in Stockholm. The Stockholm Conference was a significant international conference in which more than 6,000 people represented 113 countries, and about the same number of representatives of international organizations and 700 observers. Delegations from 400 international non-governmental organizations participated. The purpose of this conference was to pay attention to the world's environmental issues and their relationship with human rights, as well as to warn of the harmful effects of human activities on the environment.

The Stockholm Declaration of 1972 contained 26 principles. According to the declaration, environmental issues should be at the forefront of international concerns and marked the start of a dialogue between developed and developing countries on the link between economic growth, the pollution of the air, water, and oceans and the well-being of people around the world. In addition, the Action Plan contained three main categories: a) Global Environmental Assessment Programme (watch plan); b) Environmental management activities, and (c) International measures to support assessment and management activities carried out at the national and international levels. In addition, these categories were broken down into 109 recommendations. Another important outcome of the conference was the establishment of an international body called the United Nations Environment Program (UNEP). UNEP is a United Nations-affiliated environmental protection program that has been one of the most important pillars of environmental protection. One of the important tasks of UNEP is the Global Environmental Assessment, which publishes a collection annually that describes the state of the world's environment. UNEP is also coordinating and managing the world's environmental protection in cooperation with the states worldwide. According to this mandate, UNEP does not have the right to directly interfere in the environmental issues of States, but all UNEP actions are carried out with the cooperation and participation of governments at the regional and global levels. This means that the United Nations allocates funds and credits to protect the environment of countries so that these countries can take the necessary measures to protect their environment. The Stockholm Declaration has strongly influenced the further development of international environmental law.

In addition, in this generation, several international treaties, bilateral and multilateral, were signed, adopted and ratified by the States. This generation's normative and structural evolution has strongly influenced the further development of International Environmental Law.

III. Third generation: from the Rio Conference 1992 until the present
The third generation of international environmental law begins with the 1992 Rio Conference on Environment and Development. The UN General Assembly approved holding an international conference on the environment and development. Accordingly, the Conference's preparatory committee was formed with the active participation of representatives of all member states and representatives of international organizations, both governmental and non-governmental. Subsequently, the United Nations Conference on Environment and Development was held on June 3, 1992, in Rio de Janeiro, Brazil, with the participation of more than 30,000 people from 176 countries, including 116 heads of state and representatives of 1,400 international non-governmental organizations working in the field of environment. In addition, the 1992 United Nations Framework Convention on Climate Change (UNFCC) and the Convention on Biological Diversity (CBD), drafted before the Conference, were opened in Rio for signature. In discussing the issue of the environment as a global problem, the Rio Conference stressed the need to coordinate the development process of countries with the protection of the environment and introduced environmental protection as an essential international issue for the next century. The proposal to establish international environmental regulations to achieve sustainable development marked a new turning point in the process of developing international environmental law. In addition, the Conference strengthened existing institutions and created new ones to coordinate further the international community's efforts to protect the environment within the framework of international institutions. Finally, the Rio 1992 Conference concluded with the adoption of three non-binding instruments, including the Conference Final Statement as a Rio Declaration (one introduction and twenty-seven principles), Agenda 21 (Charter for the Future) and the Principles of Forest Conservation.

The Rio 1992 Declaration affirms that States should always be concerned with the environmental preoccupations in economic development and industrial growth. They should consider sustainable development as an approach in their national development plans. The States should consider the "principle of sustainable development" in the formulation of programmatic and ordinary laws, as well as in the drafting of bilateral or multilateral binding instruments. They should recognize the role of social groups and non-governmental organizations in protecting the national, regional, and global environment.

Another development of international environmental law in this period is the organization of the World Summit on Sustainable Development taking place from 26 August to 4 September 2002 in Johannesburg. The Conference announced the eight Millennium Development Goals for development, including eradicating poverty and hunger, achieving universal primary education, promoting gender equality, women's empowerment, reducing child mortality, improving mothers' status, Fighting against AIDS, malaria, and other diseases. The eight Millennium Development Goals for development are:


 * 1) to eliminate extreme poverty and hunger;
 * 2) to achieve global primary education;
 * 3) to empower women and promote gender equality;
 * 4) to reduce child mortality;
 * 5) to promote maternal health;
 * 6) to fight malaria, HIV/AIDS, and other diseases;
 * 7) to promote environmental sustainability; and
 * 8) to develop a universal partnership for development.

Twenty years after the Earth Summit on Development and the Environment in Rio in 1992, and ten years after the Sustainable Development Conference in Johannesburg, the Rio + 20 Conference in Brazil is an essential step towards consolidating sustainability and environmental protection. It is the background of economic, social and environmental development. Therefore, the international community met again on June 20-22, 2012, in Rio de Janeiro to review the 20-year achievements of the Rio Conference in the direction of sustainable development and the prospects of the agreed programs. The Rio + 20 Conference, while emphasizing the commitments made at the Rio Conference of 1992, known as Agenda 21, seeks to introduce a new type of engagement in which business, governments and civil society are vital leaders for the protection of the global environment.

The Rio + 20 conference was a new opportunity for the international community address through deliberations existing barriers to the development of international environmental law. For example, one of the most significant steps toward achieve sustainable development in the last decade (from Johannesburg 2002 to Rio 2012) was identifying the causes of recession and economic crisis in the previous decade and combining economic issues with environmental criteria.

Another remarkable event in this period is the 2030 Agenda for Sustainable Development. The purpose of this Agenda is a plan of action for sustainable development strengthening universal peace, eradicating poverty. The 17 Sustainable Development Goals and 169 targets demonstrate the scale and ambition of this new universal Agenda. It seeks to build on the Millennium Development Goals and complete what these did not achieve. It aims to realize the human rights of all and achieve gender equality and the empowerment of all women and girls. The Agenda create a balance between the three dimensions of sustainable development: the economic, social and environmental.

The 2015 Paris Agreement on climate change is another significant collective initiative by the international community to address climate change. The agreement aims to limit global warming to less than 2°C above pre-industrial levels and strives to limit temperature increase to 1.5°C. The agreement also promotes advanced climate action, including regular reporting and updating of national contributions to reducing greenhouse gas emissions, and a framework for financial and technological support for developing countries in climate mitigation and adaptation efforts.

The United Nations Human Rights Council, on October 8, 2021, adopted a resolution recognizing the human right to a clean, healthy and sustainable environment as an essential human right. While this right is already recognized in more than 150 national jurisdictions, its international recognition paves the way for its effective incorporation into international law and strengthened implementation at the national and international levels.

Therefore, the third period of the process of development of international environmental law could be called the period of realism, universalism, reforms. During this period, international environmental rules and regulations have evolved within the concept of sustainable development and, if necessary, have been amended to be in line with global realities and to be enforceable in practice, as well as to form new rules and regulations.

C. Principles of International Environmental Law
Principles of international environmental law are the basic ideas for the development of this field of law. They are general in nature, applicable to all relevant actors, and environmental protection around the world. Some of them are enshrined in the multilateral environmental agreements, and in this case, they obtain clear meaning for the specific international environmental regime. However, even if a treaty does not explicitly recognize a principle in its text, the principle still can play a role in the interpretation and development of the treaty. General environmental principles also can supplement specific rules and express gap-filling functions.

I. Principle of sovereignty over natural resources and responsibility not to cause transboundary environmental damage
The sovereignty of states in international environmental law has two bases; one is to recognize the sovereignty of states in the use of their natural resources, and the other is not to cause harm to other territories under the control of other states or areas that are not under the control of states, such as the high seas. The turning point in the principle of sovereignty is in Article 21 of the 1972 Stockholm Declaration, which, with a slight modification, was contained in the second principle of the Rio 1992 Declaration, which states: " States have, in accordance with the Charter of the United Nations and the principles of international law, the sovereign right to exploit their own resources pursuant to their own environmental and developmental policies, and the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States or of areas beyond the limits of national jurisdiction."

In this regard, the principle of sovereignty is one of the basic principles of international environmental law. In public international law, the principle of sovereignty is based on customary law. In the Trail smelter case (United States v. Canada) of 16 April 1938 and 11 March 1941, the Tribunal found that "under the principles of international law, as well as of the law of the United States, no State has the right to use or permit the use of its territory in such a manner as to cause injury by fumes in or to the territory of another or the properties or persons therein, when the case is of serious consequence, and the injury is established by clear and convincing evidence."

This principle is also affirmed in Principle  21 of the 1972 Stockholm Declaration, according to which "States have, in accordance with the Charter of the United Nations and the principles of international law, the sovereign right to exploit their own resources pursuant to their own environmental policies, and the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States or of areas beyond the limits of national jurisdiction" The evolution of the concept of "sovereignty" in international environmental law demonstrates that States have the freedom to use their territory. Still, at the same time, they have obligations under which their activities should not harm other countries or regions beyond the limits of their sovereignty. The principle of sovereignty obligates all States to preserve and protect the environment in its entirety, both for States on their territory and areas outside any national jurisdiction, such as the high seas, Antarctica or outer space.

II. Principle of cooperation
The principle of cooperation is a customary international obligation and one of the inseparable principles of the Charter of the United Nations. It is one of the features of contemporary international law. The principle of cooperation is binding in accordance with the Charter of the United Nations. Chapter IX of the Charter (Articles 55-60) affirms international economic and social cooperation. According to Article 55: “ With a view to the creation of conditions of stability and well-being which are necessary for peaceful and friendly relations among nations based on respect for the principle of equal rights and self-determination of peoples, the United Nations shall promote: a- higher standards of living, full employment, and conditions of economic and social progress and development; b- solutions of international economic, social, health, and related problems; and c- international cultural and educational cooperation; and universal respect for, and observance of, human rights and fundamental freedoms for all without distinction as to race, sex, language, or religion.” Given its transnational nature, this principle is more necessary in international environmental law because the environment has no border.

Protection of the global environment is beyond the capacity of one or more States. It requires the international community's cooperation to prevent, reduce, and eliminate the harmful effects of environmental degradation and pollution. According to the principle of cooperation, States have a duty to work together in all circumstances and in good faith to protect the environment. The obligation of cooperating in environmental issues arises from the very existence of general public international law. More than a thousand international treaties recognize the need to collaborate with other states at different levels: bilateral, regional or global. In this context, the creation of numerous international organizations also corresponds to the need for institutional cooperation in environmental protection. International conventions or treaties constitute the most effective instrument for international cooperation, mainly because their content is mandatory under the principle of Pacta sunt servanda recalled in Article 26 of the Convention of Vienna of 1969 on the law of treaties. International cooperation could be considered in various fields such as information exchange, technology transfer, financial resources, participation in international conferences, and even emergency assistance through bilateral or multilateral agreements. Although each sovereign state is free to conduct its external relations according to what it considers to be its best interests, modern international law has developed a general obligation to cooperate with others to resolve problems that concern the international community as a whole.

In addition to the general obligation of United Nations member states to cooperate in good faith with the organization and among themselves, the particular need to cooperate to preserve the environment is expressed in several legal instruments, including soft law. Moreover, cooperation in international environmental law most often emerges in the context of international organizations, whether they already exist or are created for a particular environmental issue or sector. Finally, due to the transboundary nature of the environment, states are obliged to cooperate in all circumstances in good faith to protect the environment.

III. Principle of Sustainable development
Since the late 1980s, the term sustainable development has dominated environmental law and policy. In 1987, the World Commission on Environment and Development (WCED) published the «Our common future» report. The Brundtland Report stated that critical global environmental problems were primarily the result of the enormous poverty of the South and the non-sustainable patterns of consumption and production in the North. It called for a strategy that united development and the environment – described by the now common and widespread term «sustainable development.» Sustainable development is defined as follows: «Sustainable development is a development that meets the needs of the present without compromising the ability of future generations to meet their own needs.» In 1989, the UN General Assembly debated the Report, which decided to organize a UN Conference on Environment and Development. The sustainable development principle presupposes that development policies should aim to eradicate poverty, improve economic, social and cultural conditions, preserve biological diversity, essential ecological processes, and life-sustaining systems. In addition, environmental conservation should be considered an integral part of the planning and carrying out of activities at all stages.

According to the principle, States should review national policies and plans for environment and development to enact effective laws and regulations that use economic instruments where appropriate and establish and strengthen institutional structures and procedures to integrate environmental and development issues into all decision-making spheres fully. In addition, the integration of environmental, social and economic policies also requires transparency and broad public participation in decision-making by the authorities.

The principle of sustainable development is confirmed in many international legal instruments, including the Rio Declaration of 1992. The concept of sustainable development is an evolutionary process that meets the current generation's needs without diminishing the ability of the next generation to meet their needs, in other words, to provide an opportunity for everyone to live forever on the planet. Today, sustainable development is one of the most fundamental issues of international environmental law. Without a doubt, it can be named the primary goal of the development of international environmental law.

However, the implementation of sustainable development confronted some challenges in its forms and contents. In terms of content, it lacks a comprehensive approach for including indigenous people, local cultures, good governance, consuming resources, producing goods and services, freedom of expression, employment, identifying the roots of poverty and gender discrimination.

The principle of sustainable development is a framework for economic, social, and environmental progress that seeks to meet the needs of the present without compromising the ability of future generations to meet their own needs. This principle recognizes that the long-term health and prosperity of society depend on balancing economic, social, and environmental factors, and it emphasizes the importance of responsible resource management, conservation, and equity. In this regard, Sustainable development is based on the fact any development should meet the needs of the present without compromising the ability of future generations to meet their own needs.

The three-pillar conception of sustainability (social, economic and environmental), usually represented by three intersecting circles with overall sustainability at the center, has become ubiquitous. However, some research finds that there is no single point of origin for this three-pillar conception but rather a gradual emergence of various critiques in the early academic literature of the economic status quo from the point of view. Moreover, conceptualizing the three pillars of Sustainable development is complicated in international environmental law. Nevertheless, there is a  theoretically rigorous description of the three pillars of sustainable development.

Sustainable development is based on principles such as “environmental protection” to protect ecosystems and natural resources for future generations. Secondly is based on the “precautionary approach,” which is crucial to anticipate and avoid potential environmental, economic, and social risks before they become a problem. Thirdly, it relies on “economic growth” to encourage equitable and sustainable economic development. It is crucial that economic activities not compromise the ability of future generations to meet their economic needs. Fourthly, Sustainable development depends on “social equity,” which could promote a fair and just society where all individuals have access to basic human needs such as food, water, shelter, education, and health care. Finally, it counts on “participatory decision-making”. This will assist in involving all stakeholders in the decision-making process to ensure their perspectives and concerns are considered. Finally, the principle of sustainable development emphasizes the importance of balancing economic, social, and environmental factors in all decision-making to ensure we can create a prosperous and sustainable future for ourselves and future generations.

IV. Principle of prevention
The prevention of environmental degradation and pollution is regarded as the "golden rule" in international environmental law based on economic and ecological reasons. For instance, extinction of plant or animal species, soil erosion, loss of human life and leakage of pollutants into the sea create irreparable damage in a way that, even when the damage can be compensated, restoring them to their previous state is not possible. The Prevention Principle in International Environmental Law is to prevent national and transboundary harm due to the activities of the state. Often recognized as a part of the precautionary approach or sustainable development, the prevention principle deserves more attention and investigation to clarify states’ duty and to ensure definitional clarity to other entwined norms in environmental law.

This principle forms the basis of many international environmental agreements and conventions, such as the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal (1989). The principle aims to minimize hazardous waste generation and combat illegal dumping. Many environmental laws are designed to respond to disasters, but preventing damage to the environment is cheaper and easier than replying to damage that has already occurred, and the environmental impact is less. The principle is the rationale behind international and national regulations governing the climate change, transport, treatment, storage and disposal of hazardous wastes.

V. Precautionary Principle
The precautionary principle imposes a duty on states to prevent environmental damage. Under this rule, a state may be obligated to take precautionary measures to prevent damage within its jurisdiction. The number of international environmental treaties confirms this duty of stats. In this perspective, Article 3 of the United Nations Framework Convention on Climate Change (UNFCC) states that: “''The Parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures, taking into account that policies and measures to deal with climate change should be cost-effective so as to ensure global benefits at the lowest possible cost''”.

The precautionary principle applies when there is uncertainty about the risk of environmental harm. This principle allows or requires protective measures to be taken without waiting until the harm materializes. So, it deals with potential environmental damage and serves as a tool to bridge uncertain scientific information and political responsibility. The principle has been applied globally to guide policy on issues such as chemicals and food safety, air quality or climate change. According to the EU law, it tends towards strict precaution and follows the “better safe than sorry” approach. In this regard, the EU’s environmental policies are based on a strict application of the precautionary principle, making them the most restrictive ones globally.

VI. Principle of notification
This principle is one of the basic principles that can be traced back to the International Court of Justice from the 1949 Corfu Strait case and other international sources such as environmental treaties and agreements. According to this principle, States have an obligation to notify other states in case of transboundary damages. There are also some other principles and concepts, such as the common heritage of humanity in international law and the rights of future generations. This obligation is primarily related to international cooperation based on a system of information and prior consultation and notification to achieve optimum use of natural resources without causing damage to the legitimate interests of other states. According to this principle, prior notice obligates acting States to provide timely notification and relevant information to every state that may be adversely affected by its environmental activities. states shall immediately notify other States of any natural disasters or other emergencies likely to produce transboundary effects. In addition, notification is fundamental when there is a nuclear accident and transboundary pollution.

VII. Polluter-pays Principle
The Polluter-pays Principle (PPP) is set out in many national and international regulations. According to this principle, polluters must bear the costs resulting from measures to prevent, reduce and fight pollution. This principle was adopted by the Organization for Economic Co-operation and Development (OECD) in 1972 as an economic principle for allocating the costs associated with pollution control. This is one of the essential principles underlying environmental policies in developed and developing countries. The Declaration of the United Nations Conference on Environment and Development in 1992 recognized this principle as one of the twenty-seven guiding principles for future sustainable development. According to principle 16 of the declaration, "National authorities should endeavor to promote the internalization of environmental costs and the use of economic instruments, taking into account the approach that the polluter should, in principle, bear the cost of pollution, with due regard to the public interest and without distorting international trade and investment”.

The objective of the polluter pays principle is to reduce and control the impact of human activity on the environment by promoting non-polluting activities. It means that polluters must bear the expenses relating to preventing this pollution. The international community recognized the principle in many recommendations and international treaties. The PPP is an internationally recognized environmental principle that influences the development and environmental policy at national and international levels. This principle is developed from political slogans to legal rules. In fact, the principle’s scope has expanded in recent years. Initially, it only concerned the costs of preventing and combating pollution. Then, the principle is extended to the costs of measures taken by the authorities due to pollutant emissions. Finally, it rose to environmental liability.

VIII. Principle of common but differentiated responsibilities (CBDR)
The Principle of common but differentiated responsibilities (CBDR) is one of the crucial principles of international environmental law. According to this principle, all States are responsible for protecting the environment but with different types of responsibilities. Developed countries have a more significant burden due to their historical contributions to environmental degradation. As a result, they should assist developing countries with transferring new technologies and supporting them financially. According to Principle 7 of the 1992 Rio Declaration, States should cooperate in a spirit of partnership to conserve, protect and restore the health and integrity of the Earth's ecosystem. Given the diversity of roles played in global environmental degradation, States have common but differentiated responsibilities. Developed countries recognize their responsibility in the international effort to promote sustainable development, given their societies' pressures on the global environment and the technologies and financial resources at their disposal.

One of the first legal instrument (Hard Law) which elaborate this principle is the 1992 United Nations Framework Convention on Climate Change (UNFCCC). According to this document, the Principle of Common but differentiated responsibilities is as a pathway to balance the shared responsibility of all States to address climate change. Based on this convention,  developed countries are historically responsible for greenhouse gas emissions. The principle recognizes that developed countries have benefited from exploiting natural resources and using fossil fuels, resulting in a disproportionate share of greenhouse gas emissions in the atmosphere.

This principle explains the differentiation between States by their unequal contribution to environmental degradation, on the one hand, and by the recognition that accounts must be taken of their respective economic situation, on the other. In this perspective, the principle was later included in the 1997 Kyoto Protocol, which sets binding emission reduction targets for developed countries. Based on the Kyoto Protocol, developed countries are responsible for reducing their greenhouse gas emissions by an average of 5% below 1990 levels over the period 2008-2012. In contrast, developing countries were not subject to binding emissions reduction targets but were expected to take voluntary actions to address climate change. Finally, this principle provides a pathway to balance the shared responsibility of all nations for addressing environmental issues with the recognition of historical commitment and capacity.

D. Sources of International Environmental Law
International environmental law borrows traditional sources from public international law. Thus, Article 38 of the Statute of the International Court of Justice indicates the different possible sources of public international law applicable to international environmental law. However, these sources are not limited to traditional sources of public international law. Therefore, to better understand the sources of international environmental law, it could be discussed at two different types of non-binding (soft) and binding (hard) sources:

I. Hard Law
Hard law is a binding law that imposes obligatory rules and regulations on governments to take international responsibility in environmental issues. Therefore, it is essential to consider that the sources of international environmental law go beyond public international law. International Environmental Treaties, including Multilateral Environmental Agreements (MEAs) and Bilateral Environmental Agreements (BEAs), are crucial for international environmental law's current and future development. This source of hard law aims to provide a binding legal instrument to protect the environment. Therefore, international environmental law treaties have unique characteristics compared to public international law. First, many environmental treaties aim to create a permanent structure to expand cooperation between the member states by building institutional organizations or referring to an existing international organization. Secondly, environmental treaties include executive mechanisms to implement and monitor the execution of the agreements. In addition, international environmental law treaties generally possess dispositive regarding amendment and revision. The convention-framework system is one of the unique features of international environmental treaties. This mechanism is usually about the general treaties that the States want to compile their principles and general obligations in a legal text under the convention's name and subsequently sign and approve other legal documents or texts in line with the convention's goals. This type of text is called a protocol. Convention framework exists in international environmental law more than public international law. The contracting parties reach an agreement, but the agreement details depend on future contracts negotiated and accepted under the protocol.

In addition, another source of international environmental law is international customary law. Even with the multiplication of international treaties, customary law remains crucial in this branch of law. In this context, the obligation to prevent transboundary harm and the “duty to prevent” can be considered examples of customary law. In international environmental law, customary law establishes fundamental principles and concepts. For instance, the principle of “sustainable development” reflects common development practices and the shared conviction of States to create an enabling environment for development. It also contributes to the development of international environmental law by recognizing customary principles such as common duties to prevent transboundary harm, the principle of prevention, and the principle of common but differentiated responsibilities (CBDR). These principles have been sought over time through States’ acceptance and show their customary nature. However, the customary legal status of fundamental environmental principles remains unclear, which contributes to the complexity and lack of clarity in the implementation of international environmental law.

II. Soft Law
It is essential to mention that even though soft law is not binding, it has a crucial impacts on the development of international environmental law. The most significant examples of these sources are the 1972 Stockholm Declaration, the 1982 Universal Charter of Nature, the 1992 Rio Declaration and Agenda 2030 for sustainable development. In addition, the soft law core idea is to affirm or declare general principles and define a guideline for states to protect their environment in a flexible manner.

The variations of the sources in hard law and soft law will assist the evolution of international environmental law, such as the global climate change regime. For instance, the Paris Agreement combines harder procedural commitments with softer substantive provisions, potentially encouraging flexible responses to changing conditions within a stable, long-term architecture. However, the Agreement’s softer, transparency-based compliance framework provides limited assurance that countries will make and fulfill ambitious commitments.

Nevertheless, international environmental law based on “soft law” is not only available to international judges or arbitrators. They can also be helpful for inter-State diplomacy. They may also effectively be taken into account by municipal judges in evaluating the legality, concerning international law, of any internal administrative action having had or can have some damaging impact on the environment beyond national boundaries. Furthermore, municipal judges may consider these international standards to give a correct interpretation of supremely generally formulated international obligations. Finally, the drafting and implementation of these sources of law allow governmental and non-governmental actors to cooperate together.

E. Global Environmental Problems and Challenges
Despite all global efforts, to develop binding and non-binding legal instruments, environmental concerns and threats such as global warming, climate change, desertification, and deforestation are not only remaining but also increasing.Today's world's environmental concerns and threats go beyond the predictions of the experts and scientists present at Stockholm's first environmental Conference in 1972.

I. State sovereignty
Regardless of the concept of the sovereignty of states in international law, one of the main obstacles for the development of international environmental law, is the non-acceptance of governments, to delegate or limit their sovereignty, in favour of environmental organizations. Another conflict also exists between developed and developing countries in enforcing regulations. For instance, according to the principle of Common but Differentiated Responsibilities, developed countries should take additional actions such as transferring technologies or contributing finance to developing countries, but this principle is not respected properly. This principle clearly set out in many international environmental treaties, such as United Nations Framework Convention on Climate Change (UNFCC). According to this convention, developed countries should provide financial resources to assist developing countries in implementing the objectives for protecting climate change.

II. Diversity of sources
Another substantive challenge to developing international law is the diversity of binding and non-binding sources, which is caused confusion and vagueness in the implementation of international law. The variety of binding and non-binding sources creates a significant challenge for developing and implementing international law. This diversity often leads to confusion and ambiguity in implementing international legal principles. The absence of a globally applicable environmental treaty, the limited decisions of international Courts, and the unclear customary law status of critical environmental regulations exacerbate these challenges. This problem arises because of the absence of a global environmental treaty that can serve as a binding framework for all States. In addition, the limited number of judgments from international Courts creates gaps in legal interpretation and guidance.

International environmental law has fallen between the development of general environmental principles, mainly enunciated in non-binding international instruments (such as the 1992 Rio Declaration on Environmental and Development) and binding international environmental treaties which are nevertheless sector-specific in their orientation, or even when comprehensive in their approach to (several) environmental threats, are regional in their geographical scope of application. This developmental ‘gap’ between general environmental principles and specific treaty rules points towards a substantive failing within international environmental law as a viable subdiscipline of public international law generally. The lack of general application of even cornerstone principles of and incasing new sources of international environmental law could be a normative gap in this field of law.

III. Insufficient guarantee of implementation
Many international rules and regulations, including multilateral treaties, are confronted with a deficiency of compliance mechanisms to protect the environment. The failure to provide financial mechanisms in international environmental treaties is one of the principal points of concern of the international community to implement environmental obligations, especially in developing countries. Principle 9 of the Rio Declaration stated, “States should cooperate to strengthen endogenous capacity-building for sustainable development by improving scientific understanding through exchanges of scientific and technological knowledge, and by enhancing the development, adaptation, diffusion and transfer of technologies, including new ones and innovative technologies.”

IV. Institutional challenge
Global environmental protection since the 1970s has prompted international governmental organizations to participate in environmental conservation efforts actively. As subjects of international law, these organizations have an important responsibility in this field. The 1972 Stockholm Conference reflected the growing recognition of the need for global environmental governance. It led to the establishment of the United Nations Environment Program (UNEP) as the principal body and executive for international environmental protection. However, despite its establishment, UNEP has faced limitations and challenges in effectively protecting the global environment. As environmental challenges continue to intensify and evolve, there is a growing need to assess the feasibility of creating a new organization specifically dedicated to environmental protection, such as the Organization World Environment (WEO).

Creating a WEO could fill the gaps in the existing framework by providing a dedicated institution solely focused on global environmental issues. This organization can be given resources, authority and a clear mission to address serious environmental challenges in different sectors and regions. It can also foster stronger coordination and cooperation between States, international organizations and public participation. It is essential to mention that establishing a new global organization to protect the global environment requires careful assessment and consideration of various factors, including global governance structures, international funding mechanisms, decision-making processes, and linkages to existing international organizations.

V. Emergence of environmental challenges in the world
From the early 90s, environmental threats became alarming: the destruction of the stratospheric ozone layer, climate change, sea level rise, ecosystem acidification, sheer loss of biological diversity, overexploitation of marine resources, increased technological risks, etc. The emergence of increasingly unpredictable risks enticed the authorities to base their policy on an anticipatory model. This model can be linked to understanding scientific expertise's limitations. While prevention is based on a particular risk, the new model is distinguished by the intrusion of uncertainty.

The world is confronted with several environmental problems and challenges, such as climate change, global warming, air, water, soil and light pollution, resource depletion, massive disappearance of plant and animal species, the depletion of biodiversity and other environmental degradations. These challenges could have significant implications for human health, social stability and economic development.

Climate change is one of the major challenges of the current world. According to the report released by the Intergovernmental Panel on Climate Change (IPCC) for 2022 : "Human-induced climate change is causing dangerous and widespread disruption in nature and affecting the lives of billions of people around the world, despite efforts to reduce the risks. People and ecosystems least able to cope are being hardest hit, said scientists in the latest Intergovernmental Panel on Climate Change (IPCC) report. This report is a dire warning about the consequences of inaction... It shows that climate change is a grave and mounting threat to our well-being and a healthy planet. Our actions today will shape how people adapt, and nature responds to increasing climate risks". The world faces unavoidable multiple climate hazards over the next two decades with global warming of 1.5°C (2.7°F). Even temporarily exceeding this warming level will result in additional severe impacts, some of which will be irreversible. Risks for society will increase, including to infrastructure and low-lying coastal settlements. The Summary for Policymakers of the IPCC Working Group II report, Climate Change 2022: Impacts, Adaptation and Vulnerability was approved on Sunday, February 27 2022, by 195 member governments of the IPCC.

Conclusion
Global challenges need global solutions: in this perspective, international cooperation between states plays a vital role. Economic growth and increasing technological advances in the contemporary period have caused real damage to the environment. States should be willing to participate actively in drafting, signing, ratifying and implementing new treaties on environmental issues such as water pollution and climate change in a sustainable way.

It is also crucial to recognize the right of public participation in the environmental decision-making process and implementation. The right to “environment” and right to “economic development” as a “human right” should be considered in the concept of sustainable development as a common concern of humanity. Now is the time for the international community to impose absolute responsibility or strict liability to states for any damage and harm to the environment at the national and international levels.

It is essential to note that the role of non-governmental organizations (NGOs) is crucial in the future development of international environmental law. Although the classic approach of international law recognizes mainly the role of States and governmental organizations, international environmental law recognizes that NGOs could have different roles in setting priorities and assisting in creating and enforcing national and international norms and regulations.

In the future, international environmental law will continue to develop significantly. From the 1972 Stockholm Conference, a shift occurred in the various States’ policies at the national and international levels. In this perspective, normative evaluation such as the International conventions on ozone protection (1985), the conservation of Antarctic marine fauna and flora (1980), the control of transboundary movements of hazardous wastes (1989), the Paris Agreement on climate change (2015) and many others are negotiated and ratified and enter into force within more than five decades. Regarding the structural evolution of international environmental law, the United Nations and UNEP reform are crucial for the future development of international law. Finally, international peace and security are necessary to ensure sustainable development for humanity, regardless in developed or developing countries.

Further Readings

 * Alexandre Kiss, Dinah Shelton, Guide to International Environmental Law, (Martinus Nijhoff Publishers, 2007)
 * UNEP, Training Manual on International Environmental Law, (Publication of the United Nations Environment Programme)
 * Abbas Poorhashemi, Emergence of International Environmental Law: as a new branch of International Public Law, (CIFILE Journal of International Law, Canada, V. 1, Issue 2, 2020, P. 33-39)
 * Laurence Boisson De Chazournes, La protection de l'environnement global et les visages de l'action normative internationale, (In: Mélanges en l'honneur de Michel Prieur. Paris : Dalloz, 2007. p. 41-57)
 * Philippe Sands, Jacqueline Peel, Adriana Fabra, Ruth MacKenzie, Principles of international environmental law, (Cambridge, United Kingdom ; New York, NY : Cambridge University Press, 2018)
 * Duvic-Paoli, L. (2018). The Prevention Principle in International Environmental Law. In The Prevention Principle in International Environmental Law (Cambridge Studies on Environment, Energy and Natural Resources Governance, p. Iii). Cambridge: Cambridge University Press.