From the Introduction: "Review of Clean Air Act regulations issued under the Obama Administration, with the possibility of their modification or repeal, has been a major focus of the Trump Administration since it took office in 2017. The U.S. Environmental Protection Agency (EPA) has conducted these reviews as part of the Trump Administration's 'regulatory reform' initiative under which the Administration has directed federal agencies to evaluate existing regulations and identify those that should be considered for replacement, repeal, or modification. In addition, Executive Order (E.O.) 13783 has directed EPA and other federal agencies to review existing regulations and policies that 'potentially burden the development or use of domestically produced energy resources' for consistency with policies that the E.O. enumerates, and as soon as practicable, to 'suspend, revise, or rescind the guidance, or publish for notice and comment proposed rules suspending, revising, or rescinding those rules.' EPA rules to regulate greenhouse gas (GHG) emissions from power plants, cars and trucks, and the oil and gas sector have been of particular interest."
CRS Report for Congress, R45451
Congressional Research Service: https://crsreports.congress.gov/