Not splitting hairs there is a big difference between saying a law or regulation violates the Constitution and saying it outside the scope of the legislation. HUGE difference.
They do this by first posting the proposed regulation in Federal Register. They then open the proposed regulation up to public comments. Depending on the scope and number of public comments received they set up a series of public hearings. Through the hearings process amendments are proposed and sent back to the agency. The agency then determines whether or not they want to amend the regulation. If they amend it the whole process starts over again. If they do not amend they set an effective for between 60 and 120 days for it to become effective and publish the final regulation in the Federal Register. This is well known process and is Constitutional is being carried out right now in various forms.
Once again we are told that whole process including the press coverage is some sort of liberal conspiracy...what a crock. The fact is that it was a regulation that appears to be valid that was struck down by the conservative court mainly because they didn't like it. How is that? The CAA allows the list of pollutants to be modified by administrative action.
(2) Revision of the list
The Administrator shall periodically review the list established by this subsection and publish the results thereof and, where appropriate, revise such list by rule, adding pollutants which present, or may present, through inhalation or other routes of exposure, a threat of adverse human health effects (including, but not limited to, substances which are known to be, or may reasonably be anticipated to be, carcinogenic, mutagenic, teratogenic, neurotoxic, which cause reproductive dysfunction, or which are acutely or chronically toxic) or adverse environmental effects whether through ambient concentrations, bioaccumulation, deposition, or otherwise, but not including releases subject to regulation under subsection (r) of this section as a result of emissions to the air. No air pollutant which is listed under section 7408(a) of this title may be added to the list under this section, except that the prohibition of this sentence shall not apply to any pollutant which independently meets the listing criteria of this paragraph and is a precursor to a pollutant which is listed under section 7408(a) of this title or to any pollutant which is in a class of pollutants listed under such section. No substance, practice, process or activity regulated under subchapter VI of this chapter shall be subject to regulation under this section solely due to its adverse effects on the environment.
In 2009 the EPA declared CO2 and five other greenhouse gasses a pollutant and included it on the list of pollutants in the CAA.
EPA Declares Greenhouse Gases Hazardous to People's Health and Environment - ABC News
Now I am willing to accept this ruling however dubious it is but it IS NOT a ruling on the Constitutionality of the administrative law process.