9. Clean Air Act Amendments (1970). Other landmarks of environmental legislation could easily have filled this spot — such as the National Environmental Policy Act, passed the previous year — but this measure attracted the most support among our panelists. It played a key role in the federal government’s pre-emption of state regulatory authority over the environment, and, coming shortly after the first Earth Day, it was designed to be a clear signal that environmental regulation and economic growth were not incompatible. Despite some ups and downs, that view still holds considerable sway.
10. Personal Responsibility and Work Opportunity Reconciliation Act (1996). This major overhaul of welfare, requiring work rather than government assistance, directly affected many Americans. But it was also passed by a Republican Congress and signed by a Democratic president, Bill Clinton, thus signaling the bipartisan abandonment — albeit a long time coming — of the ideas that undergirded President Lyndon Johnson’s Great Society.
Seven additional measures came very close to making the top 10. The runners-up:
• End of the military draft (1973). This one, among these measures, was a case of Congress allowing a law to expire, rather than passing something. The elimination of the draft not only began to heal perhaps the most controversial aspect of the Vietnam War, but it led directly to the creation of an all-volunteer military, which, barring an unprecedented military threat, is likely to continue into the foreseeable future.
• Gun Free School Zones Act (1990). Another oddity: This law’s significance comes not from its passage, but from its being declared unconstitutional. In United States v. Lopez (1995), the Supreme Court threw out the law as an unconstitutional exercise of power under the constitution’s Commerce Clause, thus curbing the long-exercised federal power to regulate interstate commerce. This precedent has shaped legislation and jurisprudence ever since.
• Trade Expansion Act (1962). This act set the United States firmly on the path of free trade, producing both great economic expansion and dislocation.
• Nuclear Test Ban Treaty ratification (1963). This treaty prohibited nuclear weapons tests in the atmosphere, outer space and under water. It not only curbed the spread of dangerous radioactivity in the environment, but it also set a precedent for future international accords that, in all likelihood, prevented the outbreak of nuclear war. Even as other international treaties have cracked under the strain of national interest, this one has remained rock-solid for more than four decades.
• U.S. Airline Deregulation Act (1978). The deregulation of the airlines — approved by a Democratic Congress and President Jimmy Carter — was subsequently used, primarily by Republicans, as a model for the deregulation of other sectors, including telecommunications and financial services. It became a milestone in the building of popular confidence in the private sector and dissatisfaction with government regulation.
• Comprehensive Drug Abuse Prevention and Control Act (1970). This act consolidated previous drug laws and strengthened law enforcement by allowing police to conduct “no-knock” searches. It was probably the key law in the escalation of the war on drugs — a war that remains with us 35 years later, without an end in sight.
• Amendments to the Social Security Act (1972). This act increased Social Security payments and indexed them to inflation. “It virtually wiped out homelessness among the elderly,” Mayhew said.
One additional contender earns a grade of “incomplete”:
Vice President Joe Biden waits to conduct a mock swearing-in ceremony with Sen. Brian Schatz, D-Hawaii, in the Capitol's Old Senate Chamber, December 2, 2014. Schatz was sworn in to serve the remainder of his term since he was appointed to the seat after Sen. Daniel Inouye, D-Hawaii, passed away.