Two proposed rules related to greenhouse gas (GHG) regulation under the existing federal Clean Air Act (CAA) have reportedly cleared the White House Office of Management and Budget (OMB). The two proposals are important developments in the regulation of GHG emissions from stationary sources. The “tailoring rule,” as it has come to be known would limit the permits required for stationary sources under the (CAA) Prevention of Significant Deterioration (PSD) program to new or modified sources that emit 25,000 tons of carbon dioxide equivalent (CO2e) annually, as opposed to 250 tons annually for many other pollutants under the PSD system. The consistency with the CAA has been questioned. Another proposal would amend or revoke the December 2008 memorandum issued by EPA, known by the then EPA Administrator as the “Johnson Memo,” that concluded the PSD requirements would not apply to GHG emissions the agency or Congress made the regulation of GHGs mandatory under the CAA. These two rulemakings together would be first steps in creating an EPA-based system for regulating GHG emissions.