International Environmental Law (IEL) is concerned with the attempt to control pollution and the depletion of natural resources within a framework of sustainable development. It is a branch of public international law - a body of law created by states for states to govern problems that arise between states.
IEL covers topics such as population, biodiversity, climate change, ozone depletion, toxic and hazardous substances, air, land, sea and transboundary water pollution, conservation of marine resources, desertification, and nuclear damage.

The UN Environment Assembly - the highest-level UN body ever convened on the environment - opened on 23 June 2014 at the United Nations Environment Programme (UNEP) headquarters in Nairobi. UNEA feeds directly into the General Assembly and has universal membership of all 193 UN member states as well as other stakeholder groups. With this wide reach into the legislative, financial and development arenas, the new body presents a ground-breaking platform for leadership on global environmental policy.

Key Declarations & Treaties
Declarations
Two major declarations on international enviromental law are:
1. The Declaration of the United Nations Conference on the Human Environment (the 1972 Stockholm Declaration) (UN Doc. A/CONF/48/14/REV.1 (1972). This declaration represented a first major attempt at considering the global human impact on the environment, and an international attempt to address the challenge of preserving and enhancing the human environment. The Stockholm Declaration espouses mostly broad environmental policy goals and objectives rather than detailed normative positions. The UN website provides introductory information, procedural history and preparatory documents associated with the Declaration, as well as the full text of the Declaration .
2. The Rio Declaration on Environment and Development (UN Doc. A/CONF.151/26 (vol. I)) was a short document produced at the 1992 United Nations Conference on Environment and Development (UNCED), known as the Rio Earth Summit. The Rio Declaration consists of 27 principles intended to guide future sustainable development around the world.
In 2012 the 20th anniversary of the Rio Earth Summit was commemorated by the
Rio+20 UN Conference on Sustainable Development.
Treaties
Customary law and general principles relating to the environment, such as the 'precautionary principle' and sustainable development, are evolving but it is arguable whether any have yet become normative rules. The speed with which awareness of global environmental problems has reached the international political agenda has meant that customary law has tended to take second place to treaty law in the evolution of legal norms, and treaties have been the main method by which the international community has responded to the need to regulate activities which threaten the environment. . There are hundreds of bilateral and multilateral environmental treaties creating states' rights and obligations. The UN Environment Program (UNEP) and the UN Commission on Sustainable Development have negotiated many of these treaties.

Treaties generally concern one of the following broad subjects: toxic and hazardous substances, nuclear damage, ocean and marine sources, ozone and protection of the atmosphere, pollution, biodiversity and the protection and conservation of species and wildlife, sustainable development, and trade and the environment. The Globalex Guide on International Environmental Legal Research provides a useful table of these subjects together with links to the agreements and relevant agencies.

WAYS TO IMPROVE ENVIRONMENTAL ENGAGEMENT
*Continuing to build knowledge, concern, and urgency
The fostering of knowledge, concern, and urgency that is central to getting environmental problems on the international agenda does not end once negotiations start. Activist NGOs and leader states must continue their efforts to get more states to the table, to transform reluctant states into leaders, and to get leader states to take more aggressive positions. Improved understanding by negotiators of environmental problems and their causes – whether requested from or provided by scientists and NGOs – can foster negotiations by leading states to revise their estimates of the costs of reaching, or failing to reach, agreement. Global environmental assessments (evaluations of the status, trends, causes, and impacts of an environmental problem undertaken by international groups of government and independent scientists) especially when picked up by the media, can increase pressures on negotiators. Findings from groups like the IPCC can be quite influential with those governments that view them as credible (scientifically ?accurate?), salient (relevant to current decisions), and legitimate (reflective of their interests and perspectives) (Mitchell et al., 2006b).
Before negotiations can start, interest groups must make constituencies aware of a problem, mobilize pressure on governments, and make taking action seem urgent. Once negotiations do start, environmental NGOs and corporate actors provide conduits that can keep constituencies informed about negotiation progress and negotiators informed about constituency preferences (Lipschutz and Conca, 1993; Princen and Finger, 1994: 217; Lipschutz and Mayer, 1996; Wapner, 1996). Scientists, corporate representatives, and environmental activists also can ?infiltrate? governance, joining national delegations or Negotiating solutions to international environmental problems working directly with the bureaucracies of international organizations (Haas, 1992b: 27; Raustiala, 1997b: 730). These dynamics matter because, while interest groups try to influence negotiators? views on ecological vulnerability and abatement costs, they also try to convince them that, regardless of such vulnerabilities and costs, the political costs of opposing a group?s views are greater than those of adopting its position.

*Science
Science has received particular attention as a force promoting international environmental cooperation. Although expertise is crucial to the negotiation of arms control, trade, and human rights treaties, scientific expertise wields greater influence in environmental negotiations because of science?s central role in understanding the magnitude, causes, and solutions to environmental questions. As with the need for concern in at least one country, scientific evidence suggesting that humans are contributing to some form of environmental degradation is a necessary condition for negotiations to commence. Cooperation becomes easier ?to achieve once a common or widely shared (though not necessarily accurate) understanding of the problem, its causes, and its solutions arises? (Young and Osherenko, 1993b: 19). When knowledge is uncertain but inaction threatens high costs, policy-makers may turn to scientists in ?epistemic communities? to help them identify the nature of the problem and whether, when, and what type of action to take (Haas, 1992a: 188 and 215, 1992b; Young and Osherenko, 1993b:20). Epistemic communities concerned about an environmental problem can be particularly influential – even without strong public awareness or concern – if their attempts to foster international policy do not engender strong interest-based opposition. Thus, scientists convinced governments to negotiate and adopt the Convention on Wetlands of International Importance (Wetlands Convention) in 1971, long before the development of public concern about wetland loss (Matthews, 1993).