In a keynote speech to the conservative think tank Heartland Institute, Lee Zeldin, Administrator of the Environmental Protection Agency, told attendees they should be celebrating the agency’s recent withdrawal of its 2009 determination that greenhouse gases pose a threat to human health and welfare.

The GHG Endangerment Finding was the basis for many of the EPA’s regulations of vehicles and stationary sources of pollution under the Clean Air Act, including the Phase 1-3 emissions regulations applicable to commercial trucks and engines. That decision has been challenged in court by a number of state and local governments and environmental groups.

Without this finding, EPA said it lacks statutory authority under Section 202(a) of the Clean Air Act to prescribe standards for GHG (carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons) emissions. Therefore, EPA has also repealed all GHG emission standards from its regulations for light-, medium-, and heavy-duty on-highway vehicles and engines.

EPA asserts that the Clean Air Act itself does not authorize the agency to regulate GHG emissions from new motor vehicles for the purpose of addressing global climate change, and that Congress must pass a new law if it wants the agency to regulate GHG emissions from motor vehicles.

Two separate litigation challenges have been filed in the federal court of appeals in the District of Columbia against the EPA’s recission of its GHG endangerment finding. The first case was brought by 24 state and 15 local and county governments; the second case was brought a by a number of environmental and public health organizations. The issue of the scope of the EPA’s authority to regulate greenhouse gases will likely end up in the U.S. Supreme Court.