At least 12 states are considering developing regulations for vehicle greenhouse gas emissions that would exceed federal standards. These states cannot promulgate the rules because the primary federal framework for air pollutant regulation, the Clean Air Act, reserves the federal government's right to block state efforts. Critics are charging the Bush administration with impeding the environmental progress of states and delaying meaningful regulation of vehicle emissions.

In 2002, California Gov. Gray Davis (D) signed into law the California Clean Cars law. The legislation called for state regulators to impose strict emissions standards for new vehicles beginning with model year 2009. Eleven other states (Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington) have adopted similar legislation. Various state agencies are seeking to fully enforce the Clean Cars laws, but their plans require federal approval.

The controversy raises concerns over the sovereignty of the states in pursuing environmental regulations stricter than federal standards. The supremacy clause of the U.S. Constitution reserves to the states a wide range of powers for which the federal government isn't given specific constitutional authority, but the debate over federal versus state roles has continued for most of our nation's history. In the area of environmental regulation, scholars have traditionally viewed the states as having rights to adopt standards which go beyond what the federal government has mandated.

However, the Clean Air Act includes language specifically forbidding states from pursuing emissions regulations for motor vehicles. Section 209 of the act states: "No State or any political subdivision thereof shall adopt or attempt to enforce any standard relating to the control of emissions from new motor vehicles or new motor vehicle engines." This was primarily inserted so car manufacturers did not face different standards in various parts of the country.

The act does provide a caveat allowing the federal government to waive the provision. Historically, the U.S. Environmental Protection Agency (EPA) has granted waivers to the states to allow them to implement state-specific regulations. For example, in 2006, EPA granted a waiver to California allowing the state to require on-board displays to monitor emissions from certain diesel trucks.

California requested a waiver in December 2005 in order to pursue its broader vehicle emissions plans, but EPA has yet to decide on the request. If EPA grants California a waiver, it will set the precedent for other states to request waivers to enforce stricter standards, using California's approach as a model. EPA opened the waiver request for public comment and has held two public meetings. The agency has not committed to a timetable for a decision.

Recently, the call for a decision by EPA has grown louder in light of an April 2 U.S. Supreme Court opinion , in which the court found greenhouse gas emissions from vehicles should be studied for harmful effects. If emissions are determined to be harmful air pollutants, they would require regulation under the Clean Air Act. The Bush administration had previously contended greenhouse gases could not be regulated legally under the act, so EPA's waiver authority would not have applied.

In an opinion column published in The Washington Post, Govs. Arnold Schwarzenegger (R) of California and Jodi Rell (R) of Connecticut chided the Bush administration for failing to grant or even act on the waiver request. The governors wrote, "It borders on malfeasance for [the federal government] to block the efforts of states such as California and Connecticut that are trying to protect the public's health and welfare."

California has indicated it will file suit against EPA if the agency does not decide on the waiver in the coming months. On April 25, Schwarzenegger sent a letter to EPA Administrator Stephen Johnson warning him of California's intent to sue if EPA does not make a decision by the end of October.

Critics have also charged the Bush administration with employing delay tactics on developing policies to reduce greenhouse gas emissions. By not deciding on California's request, the administration is further delaying meaningful policy on vehicle greenhouse gas emissions, which it has failed to regulate over the past six years. In a statement, Environmental Defense Senior Attorney Vickie Patton said, "It's time for this administration to give states the green light to fight global warming instead of burying their plans in bureaucracy."

The standoff between EPA and the states comes as President Bush recently signed Executive Order 13432 instructing federal agencies, including EPA, to develop emission reduction policies. Bush issued the E.O. in response to the Supreme Court ruling.

Bush's E.O. and accompanying statements outline a process for studying emission regulations for the remainder of his administration. The E.O. calls for collaboration among EPA and the Departments of Defense, Agriculture and Transportation as well as the White House Office of Management and Budget and Council on Environmental Quality.

However, at no point has the president addressed the issue of California's waiver request. Permitting the states to move forward would allow vehicle emission regulation to begin almost immediately. While the Clean Air Act does reserve the administration's right to deny California's request, environmental federalism principles, a precedent of granting waivers and the Supreme Court's decision strengthen the argument of the states.