Environmental law is a boy of law, which is a system of complex and interlocking statutes, common law, treaties, conventions, regulations and policies which seek to protect the environment which may be affected, impacted or endangered by human activities. Some environmental laws regulate the quantity and nature of impacts of human activities: for example, setting allowable levels of pollution or requiring permits for potentially harmful activities. Other environmental laws are preventive in nature and seek to assess the possible impacts before the human activities can occur.