The Environmental Protection Agency issued an Advance Notice of Proposed Rulemaking seeking public comment on whether it is appropriate to regulate greenhouse gas (GHG) emissions from automobiles under the Clean Air Act. In order to regulate automobile emissions, the EPA would first have to make a finding that all greenhouse gases endanger public health and safety and should be classified as a "pollutant."
Essentially, the EPA is ruling on whether or not GHG emissions should be classified as endangering public safety. If that finding is made, all GHGs including carbon dioxide, methane and nitrous oxide would have to be regulated under the Clean Air Act.
The problem with this approach is that once an endangerment finding is made, other provisions of the Clean Air Act are automatically triggered, creating much broader, costly regulation of other sectors of the economy, including agriculture. - Cattle News
Sounds like a pretty stupid idea.