Environmental law has evolved over the past half century from a specialty area of law to a primary element of legal practice. It has gone mainstream and now affects every aspect of law from administrative regulation to real estate to primary national and international policy on global issues. Environmental law also is related to Energy law, which is its own significant and distinct practice area. Electric power supply is the last regulated industry in the U.S., with state and federal regulatory agencies engaged in substantial regulation of price, choice of energy technologies, and terms of service. Energy law involves a combination of administrative regulatory practice, environmental, tax and corporate law practice. With fundamental deregulation of electric power in 18 states, and smart grid investment in more energy efficiency and renewable energy, the energy law field is very active and designated as a hot area of law and employment opportunities. Conventional environmental law practice includes the permitting, and enforcement, of permit emission restrictions to the air, land, and water by state and federal environmental agencies for private companies. Second, a significant aspect of environmental and energy law practice involves the setting of environmental policy, involving environmental and nongovernmental organizations, state and federal legislative committees, and private entities. There is both a domestic and international dimension to current environmental regulation. Since many pollutants have now been shown to migrate in air from California to Massachusetts, from Massachusetts to Europe, and from Japan to California, there is a cross-border and international dimension to environmental practice. The ongoing debate on global warming is one primary example of the truly international dimension of environmental challenges and policy.