Since Muskie left office as the U.S. Secretary of State, writers, historians, scholars, political analysts and the general public have debated his legacy. Particular emphasis is placed on his impact in the environmentalist and civil rights movement; bureaucratic advancement, and diplomacy. Overall supporters of Muskie point to an expansion of environmental protection, preservation, and security. Numerous historians have noted him as "the father of the 1960s environmental movement in America". His accomplishments in environmentalism established two of the foremost measures in U.S. environmental policy: the Clean Water Act Amendments of 1972 and 1977 and Clean Air Act Amendments of 1970 and 1977. His contributions to the Clean Air Act were so great that the bill was nicknamed the "Muskie Act". These two laws have been credited as the first major step to launching the wider environmentalism movement both in the U.S. and to some extent, the rest of the Free World. Harvard University law professor Richard Lazarus summarized Muskie's legislative legacy with the following: