Ferrey is professor of law at Suffolk University School of Law in Boston. He was visiting professor of law in 2003 at Harvard Law School, and is also professor of law (adjunct) at Boston University School of Law. He consults nationwide and internationally for clients in the independent power field, as legal counsel, as a project development adviser, and as an expert trial witness in these matters. He has served as an adviser on energy law to the U.S. Department of Energy, U.S. General Accounting Office, U.S. Department of Housing and Urban Development, U.S. Congress Office of Technology Assessment, U.S. Federal Trade Commission, National Renewable Resource Laboratory, and various state commissions. Ferrey has also advised and represented numerous independent power companies and real estate interests in the United States regarding asset divestiture and acquisition, greenfield power project development, and cogenerations, including permitting and regulatory compliance. He has successfully sited and permitted projects from 1–520 MW.

Ferrey has consulted extensively on international private power development outside the United States and advises the World Bank and United Nations on international energy sector privatization and independent power development in Asia and Africa. He is the author of more than 50 articles and chapters on environmental and energy law and he frequently appears as an expert witness before committees of the U.S. Congress.