A collective term describing international treaties, statutes, regulations, and common law and national legislation that operates to regulate the interaction of humanity and the natural environment, towards the purpose of human activity is called Environmental law (Akpan, 2004). Environmental impact statements have mostly been applied to individual projects and have led to various offshoot techniques, such as health impact assessments, social impact assessments, cumulative effects assessments, and strategic environmental assessments (environmental assessments of proposed policies, programs, and plans). In some cases, social and economic impacts are assessed as part of the environmental impact statements. In other cases, they are considered separately. Customary international law is unwritten and derives from the actual practices of nations over time. To be accepted as law, the custom must be long-standing, widespread, and practiced in a uniform and consistent way among nations. One example of customary international law is a nation’s right to use the high seas for fishing, navigation, overflight, and submarines. Environmental Impact Statement (EIS), formal process used to predict how a development project or proposed legislation will affect such natural resources as water, air, land, and wildlife. The environmental impact statement was first introduced in 1969 in the United States as a requirement of the National Environmental Policy Act. Since then, an increasing number of countries have adopted the process, introducing legislation and establishing agencies with responsibility for its implementation. Some customary international law has been codified in recent years. For example, the Vienna Convention on the Law of Treaties, which was approved in 1969 and took effect in 1980, codified the customary law that treaties between sovereign states are binding on their signatories and must be followed in good faith.